(ii) Multiple allelism : ABO blood groups.
Example : Sickle cell anaemia.
i. DNA recombination
ii. Mutation
1. They enable the organism to adapt themselves to changing environment.
2. They form raw material for evolution and development of new species.
| Character | Dominant Trait |
Recessive Trait |
| 1. Plant height | Tall | Dwarf |
| 2.Seed shape | Round | Wrinkled |
| 3. Seed colour | Yellow | Green |
| 4. Pod shape | Full | Constricted |
| 5. Pod colour | Green | Yellow |
| 6.Flower position | Axial | Terminal |
| 7.Flower colour | Violet | White |
1. Many varieties were available with observable and contrasting characters.
2. Peas normally self pollinate so pure lines could be obtained for experimental purpose
3. It was easily available.
4 The life span of pea is short and it produced large number of offsprings
5. They were easy to cultivate and did not require much care.
(a) Dominance and Recessive
(b) Homozygous and heterozygous
(c) Monohybrid and dihybrid.
| Dominance | Recessive |
| 1. When the allele expresses itself in both heterozygous as well as homozygous condition. | 1. When the allele expresses itself only in homozygous condition. |
| 2. The allele is unmodified and functional. | 2. The allele is modified and non-functional. |
| Homozygous | Heterozygous |
| 1.Condition where both the alleles of the gene are same. | 1.Condition where the alleles are different. |
| 2.The gametes formed from them are same. | 2. The gametes formed from them are different. |
| eg. TT or tt | eg. Tt |
| Monohybrid | Dihybrid |
| 1. When an individual is heterozygous for genes controlling one character it is called monohybrid | 1. When an individual is heterologous for genes controlling two characters it is called dihybrid. |
| 2. In F2 generation it produces a phenotypic ratio of 3:1. | 2. In F2 generation it produces a phenotypic ratio of 9:3:3:1 |
Explain the law of dominance using a monohybrid cross.
Law of Dominance states that
i. characters are present as dicrete units called Factors.
ii. Factors occur in pairs.
iii. In the condition where dissimilar factors are present one expresses itself and is called Dominant whereas the other does not express itself and is called recessive.
The law explains the expression of only one factor in a monohybrid cross.
For example
If we cross a Pure tall( TT) and a Pure dwarf (tt) with each other then in the First filial generation (F1) we get only Tall plants (Tt) even when two discrete factors T and t are present. Thus we can say that T factor is dominant over t factor as it expresses itself even in the dissimilar condition. The t factor is recessive as it expresses only in the homozygous condition (tt) in the Second filial generation where Tt and Tt are selfed.
. A Punnett square used to understand law of Dominance using monohybrid cross.
Using a Punnett Square, work out the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus.
If we cross a Bb (heterozygous male) and
BB (homozygous female) the distribution of phenotypic features in the first filial generation will be -:
Punnett Square of a cross between Bb and BB
1. Principle of paired factors.
2. Law of dominance. In a heterozygous individual only one allele is able to express its effect called dominant while the other remains hidden and is termed recessive.
3. Principle of purity of gametes. A gamete receives only one of the two
4. Principle of segregation. The two factors of a character keep their identity in an individual and do not blend. They segregate (separate) during gamete formation and are passed on to the offspring randomly after fertilization.
Briefly mention the contribution of T.H. Morgan in genetics.
Difference between gene and allele
Gene are the units of inheritance capable of transmitting genetic information and expressing the a particular trait in an organism.
whereas
Allele (allelomorphs) refers to the alternate form of a gene pair present on the same loci in the homologous chromosome. They are slightly different forms of the same gene.
(b) Reciprocal cross. These crosses involve the crosses concerning the same characters but with reversed sexes. It means if in a cross, A is used as female parent and B as a male parent, then in 2nd cross or reciprocal cross A will be used as male parent and B as female parent. Reciprocal cross is generally used to dtermine the contribution of sexes in inheritance pattern.
Define and design a test cross.
When a cross is made between tall plant with yellow seeds (TtYy) and tall plant with green seeds (Ttyy), what proportions of phenotype in the offspring could be expected to be
(a) tall and green
(b) dwarf and green ?
(a) Incomplete dominance
(b) The expected ratio will be 1 : 2 : 1.
i.e. 1 black, 2 steel-blue and 1 white.
Explain the following terms with example
(a) Co-dominance
(b) Incomplete dominance
(b) Incomplete dominance is the condition when none of the allele is completely dominant over the other and a intermediate phenotype is seen when alleles are present in heterozygous condition. eg- Flower color in Snapdragon.
| Incomplete Dominance | Co-Dominance |
| (1) Effect of one of the two alleles is more prominent. | (1) The effect of both the alleles is equally prominent. |
| (2) It produces a fine mixture or intermediate trait of the expression of two alleles. | (2) There is no mixing of the effect of the two alleles. |
| eg. flower color in Snapdragon. | eg. Co-dominanve of A and B alleles in ABO blood group system. |
Both IA and IB are dominant and express themselves over IO or i. IA and IB show co-dominance and produce different forms of sugar wheras IO or i does not produce any sugar. The Thus the phenotypes produced are -:
IAIA and IAIO Produces the phenotype of A blood group.
IBIB and IBIO produces blood group B.
IAIB produces Blood group AB .
IOIO produces Blood group O.
(a) IA IB x IBIB
(b) IAI° x IAIB
(c) IA IB x IAIB
(d) I° I° x IAIB.
(b) When a cross is made between IA I° x IA IB, then the two will have blood group A, one will have AB and one will have blood group B.
(c) When a cross is made between IA IB x IAIB, then the two individuals will have blood group AB, one will have A blood group and one will have blood group B.
(d) When a cross is made between I° I° x IAIB, then the two individuals will belong to blood group A and two to blood group B.
Child has blood group O. If the father has blood group A and mother blood group B, work out the genotypes of the parents and the possible genotypes of the other offsprings.
Since the blood group of the child is O so it must be homozygous for the allele IOIO . Since the parents have blood group A and B and produce a child with O blood group therefore they must be heterozygous that is the genotype of the father must be IAIO and genotype of the mother must be IBIO.
The genotypes of the other possible offsprings will be -:
Inheritance of blood groups
The Chromosomal theory of inheritance states that
1. Chromosomes as well as genes occur in pairs.
2. Two alleles of a gene pair are located on the homologous sites of homologous chromosome
3. The chromosome segregate and assort independently just like the genes during meiosis.
4. They recombine at the time of fertilisation in the zygote to re establish the parental chromosome number.
1. Both chrosomes and gene occur in pairs initially.
2. Two alleles of a gene pair as well as the chromosome pair segregate independently during gamete formation.
3. Different genes as well as different (non-homologous) chromosomes assort independently during gamete formation.
1.Chromosomes and genes are found in pairs in diploid cells.
2. Both chromosomes and genes segregate in meiosis I.
3. Each gamete receives only one chromosome and one allele of the gene pair.
4. Paired condition of both is restored during fertilization.
5. Both chromosomes and genes retain their individuality throughout life cycle.
(A) Complete Linkage. In this case, two or more gene are always inherited together and there is no recombination.
(B) Incomplete Linkage. In this case the genes may not be inherited together and recombination occurs in them.
Complete linkage and incomplete linkage
| Complete linkage | Incomplete linkage |
| The genes are completely linked , inherited in a set and no recombination is there. | The genes are not completely linked and reconbination may occur. |
| The gene are usually located very near to each other. | The genes may be a little far from each other. |
How is sex determined in human beings?
Sex is determined by XY type in humans.
In humans 22 pairs of chromosomes called Autosomes are present and one pair of Sex chromosomes are present.
Males have 44+XY chromosomes and they are heterozygous for sex chromosomes and produce two types of gamete one type is having 50% X-chromosome, whereas, other type is having Y-chromosome.
Female have 44+XX chromosomes and are homozygous and produce one type of gamete having X chromosome.
Therfore if the child has XY chromosomes it is a boy and if it has XX chromosomes it is a girl.
What is pedigree analysis? Suggest how such an analysis can be useful?
Types of mutation that arise due to change in structure of chromosome are.
1. Deletion- loss of a segment
2. Duplication. duplication of an segment which results in addition or gain of a segment
3. Insertion - addition of a segment.
Name the types of chromosomal disorders .
For example - Down's Syndrome in which there is a gain of extra copy of chromosome 21.
What is point mutation? Give one example.
Point mutation is the mutation or alteration in a single base pair of the DNA sequence. For example Sickle-cell anaemia in humans . In Sickle-cell anemia only a single base pair is altered which forms Valine instead of Glutamine at 6th position in the haemoglobin polypetide.
HbA peptide represents the normal peptide whereas the HbS represents the altered peptide.
(i) Klinefelter’s syndrome. Additional copy of X chromosome resulting into the condition of XXY in males.
(ii) Down’s syndrome. Trisomy of chromosome No. 21 .
(iii) Turner's syndrome - Absence of an one chromosome resulting into XO condition in females
2. Phenylketonuria: It is an autosomal recessive disorder characterised by absence of the enzyme which converts phenylalanine into tyrosine . The person shows mental retardation because of the accumulation of phenylalanine and converted into phenylpyruvic acid and other derivatives which are passed out in urine. Kidney also shows poor absorption.
1. It can be used to track and trace inheritance of a character .
2. It can be used to trace the pattern of inheritance of trait of abnormality or disease.
3. It has been used by genetic counsellors to inform the couples if they child will have any genetic defect or not.
(i) square (ii) circle (iii) solid circle or square (iv) open circle or square ?
Explain how a test cross can be conducted to distinguish between a homozygous and heterozygous dominant genotype.
Explain the law of independent assortment with a dihybrid cross.
Law of independent assortment. According to this law, the factors of different pairs of contrasting characters, do not influence each other. They are independent of one another in their assortment to form new combination during gamete formation.
If we cross ( dihybrid cross) a pea plant with yellow and smooth seeds with a pea plant with green and wrinkled seeds then we get two new combination and two parental combination in the F2 generation. Thus we can conclude that the characters assort independently and do not affect each other.
Result of dihybrid cross.
In four o’clock plants, red colour (R) is incompletely dominant over white (r), thus the heterozygous has pink colour. What will be the offspring in a cross between red flower and a pink flower plant?
In Four O' clock plant red (R)colour is incompletely dominant over white (r). So plant having pink phnotype will have Rr genotype.
We cross a red plant (RR) with pink plant (Rr) we get-:
50% plants with red flowers
50% plants with pink flowers.
A man with blood group A married a woman with B group. They have a son with AB blood group and a daughter with blood group O. Work out the cross and show the possibility of such inheritance.
D.
do not show independent assortment.A.
Antigen A and antibody BTwo heterozygous parents are crossed. If the two loci are linked what would be the distribution of phenotypic features in F1 generation for a dibybrid cross?
What are 'true breeding lines' that are used to study inheritance pattern of traits in plants?
True breeding line is one that, having undergone continuous self-pollination, shows the stable trait inheritance and expression for several generations.
How does the gene 'I' control ABO blood groups in humans? Write the effect the gene has on the structure of red blood cells.
In humans, the ABO blood groups are controlled by a gene called gene I. It has three alleles, namely IA, IB and i. Two of the three alleles IA and I B dominate over i. But IA and I B express themselves in each other’s presence and hence are co-dominant.
Showing the Genetic Basis of Blood Groups in Human Population is given as follows:
|
Allele from Parent 1 |
Allele from Parent 2 |
Genotype of offspring |
Blood type of offspring |
|
I A |
I A |
I A I A |
A |
|
I A |
I B |
I A I B |
AB |
|
I A |
i |
I A i |
A |
|
I B |
I A |
I A I B |
AB |
|
I B |
I B |
I B I B |
B |
|
I B |
i |
I B i |
B |
|
i |
i |
i i |
O |
These alleles help to determine the structure of the red blood cells. The plasma membrane of red blood cells has sugar polymers that protrude out from its surface and the kind of sugar is regulated by the gene 'I' of ABO blood group. The alleles IA and IB produce A and B types of sugar, while allele i does not produce any sugar. Thus when allele ‘IA and IA’ and ‘I A and i‘ are present together then the red blood cells have sugar A on the surface. When IB and I B or IA and i are present then sugar B is found on the surface. When IA and I B are present both A and B sugar are found on the cell surface. While blood group O does not bear any sugar.
Write the types of sex-determination mechanisms the following crosses show. Give an example of each type
(i) Female XX with Male XO
The type of sex determination mechanism shown in female XX with male XO is male heterogamety
Example - Grasshopper
Write the types of sex-determination mechanisms the following crosses show. Give an example of each type
(ii) Female ZW with Male ZZ
The type of sex determination mechanism shown in female ZW with male ZZ is female heterogamety.
Example - Birds
A colour-blind child is born to a normal couple. Work out a cross to show how it is possible. Mention the sex of this child.
Colour blindness is a sex-linked disease. The gene for this disorder is present on the X chromosome. If a colour-blind child is born to a normal couple, then the mother would be a carrier of the disease. The child would be male. The following cross shows the inheritance of the disorder:
Mendel published his work on inheritance of characters in 1865, but it remained unrecognized till 1900. Give three reasons for the delay in accepting his work.
The following are the three reasons that led to the delay in accepting Mendel's work:
i) Lack of communication and publicity.
ii) His concept of factors (genes) as discrete units that did not blend with each other was not accepted in the light of variations occurring continuously in nature.
iii) Mendel's approach to explain biological phenomenon with the help of mathematics was also not accepted
A geneticist interested in studying variations and patterns of inheritance in living beings prefers to choose organisms for experiments with shorter life cycle. Provide a reason.
A geneticist interested in studying variations and patterns of inheritance in living beings refers to choose organisms for experiments with shorter life cycle because it allows them to study many generations of the organisms in a short span of time.
A teacher wants his/her students to find the genotype of pea plants bearing purple coloured flowers in their school garden. Name and explain the cross that will make it possible.
Purple colour is a dominant phenotype in pea plants. To determine the genotype of the pea plant with purple flowers the students can use the process of Test cross. In test cross the pea plant whose genotype is to be determined is crossed with a homozygous recessive parent (pp) having white flowers. The test cross help the students to determine whether the genotype of the plant is heterozygous dominant (Pp) or homozygous dominant (PP).
So the Pea plant with an unknown genotype i.e. Px that can be either Pp or PP is crossed with homozygous recessive parent i.e. pp.
If half of the flowers are purple and the other half is white then the genotype of the plant is heterozygous dominant that is Pp
If all the flower produced after the cross are purple then the genotype would be PP homozygous dominant.
Explain the genetic basis of blood grouping in human population.
In humans, the blood groups are controlled by a gene called gene I. It has three alleles, namely IA, IB and i. The plasma membrane of the red blood cells has sugar polymers that protrude from the surface and the kind of sugar is controlled by the gene. The alleles IA and IB produce a slightly different sugar while i do not produce any sugar. Since humans are diploid, each person can have different combinations of the three alleles. The alleles IA and IB are dominant over i therefore a combination of IA and iproduce blood group A, IB and I produce blood group B. The combination of IA, IB produces blood group AB which has both A and B types of sugar, because of co-dominance. The combination of IA and IA produce blood group A, IB and IB produce B blood group.
The type of blood group produced by the different combinations is shown in the table below:
In a cross between two tall pea plants some of the off-springs produced were dwarf. Show with the help of Punnett square how this is possible.
The two tall plants need to be heterozygous in nature to produce a dwarf plant. The parents should have Tt genotype. They form two types of gametes T and t , from which t and t combine and form a dwarf plant.
(a) Why is human ABO blood group gene considered a good example of multiple alleles?
(b) Work out a cross up to F1 generation only, between a mother with blood group A (Homozygous) and the father with blood group B (Homozygous). Explain the pattern of inheritance exhibited.
(a) ABO blood group is considered a good example of multiple alleles as it is controlled by I gene which has 3 alleles IA, IB and i. The three alleles govern the same character and hence show multiple allelism.
(b) Homozygous mother having blood group A will have a genotype of- IAIA
Homozygous father having blood group B will have a genotype of- IBIB
A cross between
Thus the progeny will havethe blood group AB (genotype IAIB) as the alleles A and B are co-dominant to each other that is they express themselves independently even in the presence of other. Thus the progeny resembles both the parents. The pattern of inheritance is called co-dominance pattern of inheritance.
A child by the family from Thalassemia is born to a normal couple. But the mother is being blamed by the family for delivering a sick baby. (a) What is Thalassemia?
(b) How would you counsel the family not to blame the mother for delivering a child suffering from this disease? Explain.
(c) List the values your counseling can propagate in the families.(a) Thalassemia - is an autosomal recessive blood disease which can occur due to deletion of the genes controlling the formation of globin chains (commonly Alpha and Beta) of haemoglobin.
(b) Mother cannot be blamed for the disease as, it is an autosomal recessive blood disorder. The genes for the synthesis of globin chains are present on autosomes.
(i) Formation of Alpha chain is controlled by 2 genes present on chromosome 16 and
(ii) Formation of Beta-chain is controlled by one gene present on chromosome 11manifestation of the disease occurs when the progeny receives defective genes from both the parents (as thalassemia is expressed is homozygous recessive condition only).
(c) Values that can be propagated in families are
(i) One should be aware of such autosomal diseases and should get themselves checked for the same before marriage.
(ii) Manifestation of the disease occurs due to defective genetic set up of both the parent (so it is not only that the mother should be blamed.A garden pea plant (A) produced inflated yellow pod, and another plant (B) of the same species produced constricted green pods. Identify the dominant traits.
In the garden pea plant the dominant traits are:
Inflated pod and green colour of the pod.
What is the inheritance pattern observed in the size of starch grains and seed shape of Pisum sativum? Workout the monohybrid cross showing the above traits. How does this pattern of inheritance deviate from that of Mendelian law of dominance?
The starch synthesis in pea plants is controlled by a single gene. It has two alleles B and b. BB homozygotes produce starch effectively and therefore produce large starch grains. Whereas the bb homozygotes are less efficient in starch production and hence produce smaller grains. After maturation the BB seeds were found to be round and bb was wrinkled. Heterozygotes produce round seeds, and so B was considered to be the dominant allele. But when they were crossed the resultant progeny were intermediate-sized Bb seeds.
P generation BB × bb
↓
F1 Generation Bb × Bb
|
|
B |
b |
|
B |
BB (long grains) |
Bb (intermediate grains) |
|
b |
Bb (intermediate grains) |
bb (small grains)
|
Aneuploidy results in the loss or gain of chromosome during cell division.
Dominance: is the condition when in a pair of dissimilar factors or alleles, one dominates the other that is one allele expresses itself in the presence or absence of the other allele. For example, the allele for tall trait T is dominant over the trait for dwarfness t.
Co-dominance: Co-dominance is the phenomenon in which both the alleles of a contrasting character are expressed in heterozygous condition. Both the alleles of a gene are equally dominant. ABO blood group system is an example of co-dominance.
Incomplete dominance: Incomplete dominance is a phenomenon in which one allele shows incomplete dominance over the other member of the allelic pair for a character. For example, a monohybrid cross between the plants having red flowers and white flowers in Antirrhinum species will result in all pink flower plants in F1generation.
(a) Sickle celled anaemia in humans is a result of point mutation. Explain.
(b) Write the genotypes of both the parents who have produced a sickle celled anaemic offspring.
(a) Sickle cell anaemia in humans is a result of point mutation because a single base change in the gene for beta globin chain results in the change of amino acid residue glutamate to valine leads to the replacement of GAG by GUG codon at sixth position.
(b) Genotypes of parents who have produced a sickle celled anaemic offspring can be either
HbA/ Hbs and HbA/ Hbs
or, Hbs/ Hbs and HbA/ Hbs
How many chromosomes do drones of honeybee possess? Name the type of cell division involved in the production of sperms by them.
Drones of honey bees are haploid and possess 16 chromosomes.
Drones produce sperms by mitosis.
In this case,
There are 2 tall plants having genotype Tt.
And two dwarf plants having genotype tt.
Ratio of tall: dwarf = 2:2
Thus, the progeny would be 50% tall and 50% dwarf, that is tall and dwarf plants are in equal ratios.
(a) Why are thalassemia and haemophilia categorized as Mendelian disorders ? Write the symptoms of these diseases. Explain their pattern of inheritance in humans.
(b) Write the genotypes of the normal parents producing a haemophilic son.
(a) Thalassaemia and haemophilia are categorised as Mendelian disorders because they occur by mutation in a single gene. Their mode of inheritance follows the principles of Mendelian genetics. Mendelian disorders can be
Symptoms of Thalassaemia
Symptoms of Haemophilia
Pattern of Inheritance of Thalassaemia
Pair of alleles HbA and HbT controls the expression of this disease.
Conditions for thalassemia:
|
Parents |
|
HbAHbT |
x |
HbAHbT |
|
Offsprings |
HbAHbA |
HbAHbT |
HbAHbT |
HbTHbT |
|
Parents |
|
XY |
x |
XhX |
|
Offspring |
XhX |
XX |
|
XY |
|
Parents |
|
XY |
x |
XhX |
|
Offspring |
XhX |
XX |
|
XY |
Mention any two contrasting traits with respect to seeds in pea plant that were studied by Mendel.
The two contrasting traits with respect to seeds in pea plant that were studied by Mendel are:
Seed shape - Round seeds and Wrinkled seeds.
Seed colour- Yellow and Green.
In Snapdragon, A cross between true breeding red flower (RR) plants and true breeding white flower (rr) plants showed a Progeny of plants with all pink flowers.
(a)The appearance of pink flowers is not known as blending. Why?(b)What is the phenomenon known as?
(a) The appearance of pink color is not caused as blending because the alleles do not mix or blend and they maintain their originality and reappear in F2 generation. The pink color appears just because the Dominant allele is not completely dominant over the recessive allele for colour.
(b) The phenomenon is called incomplete dominance.
Linkage or crossing-over of genes are alternatives of each other. Justify with the help of an example.
Linkage is the tendency for two or more non-allelic genes to be inherited together, because they are located more or less closely on the same chromosome.
Crossing over is the process by which two homologous chromosomes pair up and exchange sections of the coiled DNA.
If linkage is high the crossing over will be low.
If linkage is less the crossing over will be more.
In Drosophila a yellow bodied white eyed female was crossed with brown bodied red eyed male, F1 progeny produced and intercrossed the F2 phenotypic ratio of Drosophila deviated significantly from Mendel’s 9:3:3:1, the genes for eye colour & body colour are closely located on the ‘X’ chromosome showing high linkage & therefore inherited together, recombinants were formed due to crossing over but at low percentage.
Why is pedigree analysis done in the study of human genetics? State the conclusions that can be drawn from it.
Pedigree analysis is done to study the human genetics because it provides a strong tool, which can be utilised to trace the inheritance of a specific trait, abnormality or disease. Since certain disorders are inheritable and also depends on the genetics of the families and the genes inherited from them thus pedigree analysis is done to trace such inheritance patterns.
The conclusions that can be drawn from the pedigree analysis are:
i. The pattern of inheritance and tracing of Mendelian disorders.
ii. Whether the trait in question is dominant or recessive.
iii. Whether the trait is linked to the sex chromosomes or autosomes.
Identify ‘a’, ‘b’, ‘c’, ‘d’, ‘e’ and ‘f’ in the table given below :
|
No. |
Syndrome |
Cause |
Characteristic of affected individuals |
Sex Male/Female/ both |
|
1 |
Down’s |
Trisomy of 21 chromosome |
‘a’ (i) (ii) |
‘b’ |
|
2 |
‘c’ |
XXY |
Overall masculine development |
‘d’ |
|
3 |
Turner |
45 with XO |
‘e’ (i) (ii) |
‘f’ |
|
No. |
Syndrome |
Cause |
Characteristic of affected individuals |
Sex Male/Female/ both |
|
1 |
Down’s |
Trisomy of 21 chromosome |
‘a’ (i) Furrowed tongue (ii) Partially open mouth, short stature |
‘b’ - Both |
|
2 |
'c' Klinefelter syndrome |
XXY |
Overall masculine development |
‘d’ - Male |
|
3 |
Turner |
45 with XO |
‘e’ (i) Sterile female with rudimentary ovaries (ii) Lack of secondary sexual characters |
‘f’ - Female |
Name the respective pattern of inheritance where F1 phenotype
(a) does not resemble either of the two parents and is in between the two.
(b) resembles only one of the two parents.
(a) Incomplete Dominance is the condition in which the F1 phenotype does not resemble both the parents and is in between the two.
(b) Complete Dominance is the condition in which the F1 phenotype resembles the dominant parent i.e one of the two parents.
(a) Explain the phenomena of multiple allelism and co-dominanace taking ABO blood group as an example.
(b) What is the phenotype of the following:(i) IAi
(ii) i i
(a) The inheritance of ABO blood groups in humans exhibits co-dominance and multiple allelism.
Multiple allelism-: The ABO blood groups are controlled by the gene I. The I gene has three alleles, namely IA, IB and i. Since more than two alleles control a single trait thus it shows multiple allelism.
Co-dominance-: The allele IA and IB are both dominant over the allele i but they express themselves completely even in the presence of the other that is when both are present the blood group is AB . This represents co-dominance.
(b) ( i) Phenotype of IAi will be A blood group since the allele IA is dominant over the allele i
(ii) Phenotype of ii will be O blood group since the allele is recessive and expresses itself in the homozygous condition.(a) Explain a monohybrid cross taking seed coat colour as a trait in Pisum sativum. Work out the cross upto F2 generation.
(b) State the laws of inheritance that can be derived from such a cross.
(c) How is the phenotypic ratio of F2 generation different in a dihybrid cross?
(a) Monohybrid cross is the cross in which only one trait is taken into account.
For example, if pea plant with yellow seed coat is crossed with pea plant having green seed coat then in the F1 generation all the plants produce yellow seeds.
(b) Two laws can be derived from such a cross
Law of Dominance- According to this law, characters are controlled by discrete units called factors, which occur in pairs with one member of the pair dominating over the other in a dissimilar pair. It explains the expression of only one of the parental character in F1generation and expression or appearance of both in F2 generation.
In the given cross, the allele for yellow seeds is dominant over the allele that produces green seeds. In F1 generation all offsprings showed yellow colour of seed (dominant character) and expression of both yellow and green in F2 generation.
Law of Segregation-This law states that the two alleles of a pair segregate or separate during gamete formation such that a gamete receives only one of the two factors. In homozygous parents, all gametes produced are similar; while in heterozygous parents, two kinds of gametes are produced in equal proportions. The alleles for yellow and green seeds in the F1 generation segregate and the gamete either contains yellow allele or green allele giving rise to different combination in the F2 generation. Thus, showing that the gametes receive only one of the two factors.
(a) Why is fertilization in an angiosperm referred to as double fertilisation? Mention the ploidy of the cells involved.
(b) Draw a neat labeled sketch of L.S. of an endospermous monocot seed.
(a) Double fertilization is a characteristic feature of flowering plants or angiosperms. In the process of double fertilization, out of the two sperm nucleus, one sperm nucleus fuses with the egg nucleus to form an embryo (process is called syngamy) and another fuses with polar nuclei to form endosperm (process is called triple fusion). Since two kinds of fusion; syngamy and triple fusion take place, the process is known as double fertilisation.
Ploidy of the cells involved
|
Cell |
Ploidy |
|
Egg cell |
Haploid |
|
Both Male nuclei |
Haploid |
|
Central cell |
Diploid |
|
Zygote |
Diploid |
|
Endosperm |
Triploid |
(b) L.S of endospermous monocot seed
A male honeybee has 16 chromosomes whereas its female has 32 chromosomes. Give one reason.
Male honeybees are born from unfertilised eggs by the process known as parthenogenesis where as female honeybees are born from fertilised eggs. As unfertilised eggs carries only half number of chromosome as compared to fertilised eggs, therefore male honeybee has 16 chromosomes whereas female has 32 chromosomes.
What is a test cross? How can it decipher the heterozygosity of a plant?
Test cross is a cross between an organism with unknown genotype and recessive parent
It is used to determine whether the Individual is homozygous or hetrozygous for a trait If the progeny produced by a test cross show 50% dominant trait and 50% recessive trait then unknown individual is hetrozygous for a trait on other hand if the progeny produced shows dominant trait then the unknown individual is homozygous for trait.
(a) What is polygenic inheritance ? Explain with the help of a suitable example.
(b) How are pleiotropy and Mendelian pattern of inheritance different from polygenic pattern of inheritance ?
(a) Polygenic inheritance is an inheritance pattern controlled by three or more genes (multiple genes) and the graded phenotypes are due to the additive or cumulative effect of all the different genes of the trait. An example of human skin colour to understand the phenomenon of polygenic inheritance. Skin colour in humans is caused by a pigment called melanin. The quantity of melanin is due to three pairs of polygenes (A, B and C).
Black or very dark is represented by (AA BB CC) and
White or very light is represented by (aa bb cc).
Individuals with the genetic constitution (Aa Bb Cc) have an intermediate colour often called mulatto .
A total of eight allele combinations is possible in the gamets forming 27 distinct genotypes distributed into 7 phenotypes, i.e. very dark, dark, fairly dark, intermediate,fairly light and very light.
(b) In Mendelian inheritance, only one gene controls one trait. Ogenegen may have two different forms of an allele. However, in Polygenic there is more than one gene controlling one trait.
For example, the gene of tallness in the case of Mendelian character has two form of the allele, both of which affect the height of the plant.
In the case of skin colour three genes A, B and C control the skin colour.
In Pleiotropy one gene affects more than one phenotype or trait. However in polygenic inheritance more than one gene controls or affects one phenotype.
In case of the amino acid tyrosine. It is needed for general protein synthesis, and it is also a precursor for several neurotransmitters (e.g., dopamine, norepinephrine), the hormone thyroxine, and the pigment melanin. Thus, mutations in any one of the genes that affect tyrosine synthesis or metabolism may affect multiple body systems. These and other instances in which a single gene affects multiple systems and therefore has widespread phenotypic effects.
State a difference between gene and an allele.
| Gene | Allele |
| Gene is a unit of inheritance that is transferred from the parent to the offspring. | Allele is the alternative form of a single gene that lie on the same locus in the homologous chromosomes. |
Give an example of an autosomal recessive trait in humans. Explain its pattern of inheritance with the help of a cross.
Sickle Cell Anaemia is an autosomal recessive trait in humans. The genes responsible for this disease are located in autosomes. The disease being recessive the trait should be present in homozygous condition, for it to express.
People who carry a single copy of the gene are clinically normal but are carriers of the disease and can pass on the defective gene to their subsequent generation.
Describe the mechanism of pattern of inheritance of ABO blood groups in humans.
In humans, the ABO blood groups are controlled by a gene called I gene. It has three alleles, namely IA, IB and i. A person possesses any two of the three alleles. IA and IB dominate over i. But with each other, IA and IB are co-dominant that is they both get expressed when present together.
IA and IB are responsible for the production of antigen A and B present on the surface of RBC. Plasma membrane of RBC possess sugar polymer that protrudes out of its surface and the type of sugar present on the surface is controlled by gene I. IA and IB allele is responsible for coding for glycosyltransferase enzyme responsible for developing modification in the terminal sugar molecule. IA and IB differ very minutely on the sugar molecule while gene i does not produce any sugar molecule. Here allele A and B are dominant in nature while ii fail to produce any antigenic molecule so express blood group O. 
A. Why is haemophilia generally observed in human males? Explain the conditions under which a human female can be haemophilic.
B. A pregnant human female was advised to undergo M.T.P. It was diagnosed by her doctor that the foetus she is carrying has developed from a zygote formed by an XX egg fertilized by Y-carrying sperm. Why was she advised to undergo M.T.P.?
A. Haemophilia is sex-linked recessive disease; it is transmitted from unaffected female carrier to male child with haemophilia. It is an X-linked recessive gene.
The females have XX condition and thus may be heterozygous carrying one normal X chromosome and diseased/affected X. Since the disease is a recessive one, therefore, it does not express until it is present in the homozygous condition.
The males have XY condition. The presence of the diseased allele of X will result in the person to develop the disease. The Y has no allele for this disease. Thus the probability of the males getting affected is much more than the females.
B. MTP stands for medical termination of pregnancy (MTP) or it may be called as abortion in common language.
The egg usually has one of the two X-chromosomes, but in this case, the pregnant female has egg having XX condition. The doctor advises for M.T.P. because her foetus may be carrying an abnormal number of chromosomes as the fertilisation of the XX egg by the Y sperm will create a trisomy condition.
During a medical investigation, an infant was found to possess an extra chromosome 21. Decribe the symptoms the child is likely to develop later in the life.
An additional copy of chromosome number 21 (trisomy of chromosome number 21) in humans results in Down’s syndrome.Following characteristic symptoms are likely to develop in the child due to the above mentioned conditions:
(i) Short statured with small, round head.
(ii) Furrowed tongue and partially open mouth.
(iii) Broad palm with characteristics palm crease.
(iv) Slow mental, physical and psychomotor development.
State and explain the ‘law of independent assortment’ in a typical Mendelian dihybrid cross.
Law of Independent Assortment (Third law) is based on inheritance of two genes, i.e. dihybrid cross which states that when two pairs of contrasting traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters. These factors randomly rearrange in the offspring producing both parental and new combination of characters means inheritance of one character does not affect the inheritance of another character and both characters
assort independently. The Punnett square can be used to understand the independent segregation of the two pairs of genes during meiosis. Linkage is the exception of law of independent assortment.
What is incomplete dominance?
The phenomenon in which neither of the alleles is dominant over the other and the offspring exhibits a phenotype intermediate between the parents
eg; flower color in snapdragon
Explain sex determination in bees.
In honeybees (or honey bees), sex is normally determined by the fertilization or non-fertilization of eggs, rather than the presence or absence of sex chromosomes. This mode of sex determination was first discovered by Johann Dzierzon, a Catholic priest, in 1845. Dzierzon reported that a virgin queen which has not taken a mating flight (the queens mate only while in free flight away from nest) produces only male progeny. His report was the first rigorous description of a sex determination system, occurring more than 50 years before the discovery of sex chromosomes. We now know that honey bees are not unique and that about 20% of animal species use a haplodiploid mode of reproduction. In haplodiploid systems, male progeny normally develops from unfertilized eggs, which are haploid and have just one set of chromosomes. The fertilized honey bee eggs, which are diploid and have two sets of chromosomes, differentiate into queens and worker bees.
Both Haemophilia and Thalassemia are blood related disorders in humans. Write their causes and the difference between the two. Name the category of genetic disorder they both come under.
Both are Mendelian disorders.
* Haemophilia is a sex linked recessive disorder. The gene for haemophilia is located on X-chromosome. The gene passes from a carrier female to her son.
* Thalessemia is an autosomal linked recessive disease.
* It occurs due to either mutation or deletion resulting in reduced rate of synthesis of one of globin chains of haemoglobin.
* The difference between Haemophilia and Thalessemia is : - In haemophilia, clotting is affected, i.e. there can be a non-stop bleeding even after a minor cut.
* In Thalessemia, anaemia is the characteristic of this disease
(a) Write the desirable characters a farmer looks for in his sugarcane crop. (b) How did plant breeding techniques help north Indian farmers to develop cane with desired characters ?
(a) The desirable characters that should be present in sugarcane crop are : - (a) High yield (b) Thick stem (c) High sugar content (d) ability to grow in North India.
(b) With the help of plant breeding, the two varieties of sugarcane i.e. Saccharum barberi [sugarcane of North India] and Saccharum officinarum [sugarcane of South India] were crossed to obtain sugarcane varieties having desirable qualities. So that a good quality sugarcane variety could be grown in North India.
Explain the mechanism of ‘sex determination’ in birds. How does it differ from that of human beings?
In birds, sex determination is of ZW – ZZ type.
In this type, the males are homogametic and have ZZ sex chromosomes, and females are heterogametic with ZW pair of sex chromosomes.
| Parents: | Male | X | Female |
| ZZ | ZW | ||
| Gametes: | (Z)(Z) | (Z)(W) | |
| F1: | ZW | ZZ | |
| Female | Male |
whereas, in human beings, the chromosomal mechanism of sex determination is of XX – XY type. The human male is heterogametic and has XY sex chromosomes and the human female is homogametic with XX sex chromosomes.
a) Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked with for their experiments. Explain the correlation between linkage and recombination with respect to genes as studied by them.
b) How did Sturtevant explain gene mapping while working with Morgan?
a) Drosophila melanogaster :
Morgan carried out several dihybrid crosses in Drosophila to study gens that were sex-lined.
Morgan and his group knew that the genes were located on the X chromosome and saw quickly that when the two genes in a dihybrid cross were situated on the same chromosome, the proportion of parental gene combinations were much higher than the non-parental type. Morgan attributed this due to the physical association or linkage of the two genes and coined the term linkage to describe this physical association of genes on a chromosome and the term recombination to describe the generation of non-parental gene combination. Morgan and his group also found that even when genes were grouped on the same chromosome, some genes were very tightly linked (showed very low recombination) while others were loosely linked.
b) Morgans student Alfred Sturtevant used the frequency of recombination between gene pairs on the same chromosome as a measure of the distance between genes and ‘mapped’ their position on the chromosome. Today genetic maps are extensively used as a starting point in the sequencing of whole genomes.
A tall true breeding garden pea plant is crossed with a dwarf true breeding garden pea plant. When the F1 plants were selfed the resulting genotypes were in ratio of
1:2:1 :: Tall heterozygous: Tall homozygous: Dwarf
3:1:: Tall: Dwarf
3:1:: Dwarf: Tall
1:2:1 :: Tall homozygous : Tall heterozygous: Dwarf
D.
1:2:1 :: Tall homozygous : Tall heterozygous: Dwarf
Parents TT (Pure Tall) * tt (Dwarf)
F1 generation
Tt ( hetrozygous tall)
Tt * Tt (selfed)
| T | t | |
| T | TT | Tt |
| t | Tt | tt |
Pick out the correct statement.
I. Haemophilia is a sex-linked recessive disease
II. Down's syndrn=me is due to aneuploidy
III. Phenylketonuria is an autosomal recessive gene disorderIv. Sickle cell anaemia is an X-linked recessive gene disorder
II and IV are correct
I, III and IV are correct
I, II and III are correct
I and IV are correct
C.
I, II and III are correct
Sickle cell anaemia is an autosomal recessive disorder
In a test cross involving F1 dihybrid flies, more parental-type offspring were produced that the recombinant type offspring. This indicates
chromosomes failed to separate during meiosis
the two genes are linked and present on the same chromosome
both of the characters are controlled by more than one gene
the two genes are located on two different chromosomes
B.
the two genes are linked and present on the same chromosome
When two genes are linked they are inherited together and result in the increase in the appearance of the parental characters.
Match the terms in Column I with their description in Column II and choose the correct option.
| Column I | Column II |
| A. Dominance | 1. Many genes governs a single character |
| B. Codominance | 2. In a heterozygous organism, only one allele expresses itself |
| C. Pleiotropy | 3. In a heterozygous organism both alleles express themselves fully |
| D. Polygenic inheritance | 4. A single gene influences many characters |
| A | B | C | D |
| 2 | 3 | 4 | 1 |
| A | B | C | D |
| 4 | 1 | 2 | 3 |
| A | B | C | D |
| 4 | 3 | 1 | 2 |
| A | B | C | D |
| 2 | 1 | 4 | 3 |
A.
| A | B | C | D |
| 2 | 3 | 4 | 1 |
Dominance is when only one gene expresses itself in the heterozygous condition.
Co-dominance is when both the genes express in the heterozygous condition.
Pleiotropy is when a single gene controls more than one phenotype.
Polygenic inheritance is when a single trait is controlled by many genes
Which of the following most appropriately describes haemophilia?
Chromosomal disorder
Dominant gene disorder
Recessive gene disorder
A.
Haemophilia is a sex-linked that is X-linked recessive disorder.
Which of the following statements is not true for cancer cells in relation to mutations?
Mutations destroy telomerase inhibitor
Mutations inactivate the cell control
Mutations inhibit production of telomerase
Mutations in proto-oncogenes accelerate the cell cycle
C.
Mutations inhibit production of telomerase
Cancerous cells have a high telomerase activity.
Which of the following statements is not true of two genes that show 50% recombination frequency?
the genes may be on different chromosomes
the genes are tightly linked
the genes show independent assortment
If the genes are present on the same chromosome, they undergo more than one crossovers in every meiosis
B.
the genes are tightly linked
The tightly linked genes on chromosomes show 100% parental types and 0% recombinants. Two genes that undergo independent assortment indicated by a recombination frequency of 50% are either on non-homologous chromosomes are located far apart on a single chromosome. As the distance between two genes increases, crossover frequency increases. More recombinant gametes, fever parental gametes.
Variation in gene frequencies within populations can occur by chance rather than by natural selection. This is referred to as
genetic flow
genetic drift
random mating
genetic load
B.
genetic drift
Genetic drift is a random change in allele frequencies over the generations. It is brought by chance alone. Gene flow or gene migration is the physical movement of alleles into and out of a population.
The existence within the population of disadvantage alleles in heterozygous genotypes is known as genetic code.
If two persons with 'AB' blood group marry and have sufficiently a large number of children, these children could be classified as 'A' blood group in 1:2:1 ratio. The modern technique of protein electrophoresis reveals the presence of both 'A' and 'B' type proteins in 'AB' blood group individuals. This is an example of
codominance
incomplete dominance
partial dominance
complete dominance
A.
codominance
In codominance, both alleles of a pair express themselves fully in F1 hybrid. It is contrary to the situation seen in incomplete dominance. where traits express themselves only partially. This is not the example of partial dominance or complete dominance.
AB→ |A|B →antigen A +Antigen B →Codominance.
The incorrect statement with regard to haemophilia is
It is a sex - linked disease
It is a recessive disease
It is dominant disease
a single protein involved in the clotting of blood is affected
C.
It is dominant disease
Haemophilia is a sex-linked recessive disease.
A single protein that is a part of the cascade of protein is involved in the clotting of blood is affected. The heterozygous female for haemophilia may transmit the disease to sons.
If both parents are carriers for thalassemia, which is an autosomal recessive disorder, what are the chances of pregnancy resulting in an affected child?
No Chance
50%
25%
100%
C.
25%
Thalassemia is the disorder due to reduced synthesis of either the alpha or beta chains, likewise designated as alpha or beta - thalassemias. When this autosomal mutant gene is present in a double dose. The disease is severely called as thalassemia major.
Which enzyme/s will be produced in cell in which there is a non-sense mutation in the lac Y gene?
beta - galactosidase
Lactose permease
Transacetylase
A.
beta - galactosidase
Beta - galactosidase is a structural gene present in the segment of DNA, which carry lcdes for the synthesis of protein. Mutation in the lac Y gene of E, coil needs residues of cytoplasmic enzyme beta - galactosidase. Lactose permease is a membrane protein, which is a major facilitator superfamily. Transacetylase is an enzyme transferring acetyl, group from one compound to another.
A gene showing codominance has:
One allele dominant on the other
alleles tightly linked on the same chromosome
alleles that are recessive to each other
both alleles independently expressed in the heterozygote
D.
both alleles independently expressed in the heterozygote
A gene shows codominance when both alleles in heterozygous condition, express their traits independently instead of showing dominant-recessive relationship and such alleles are called codominant alleles.
The term 'linkage' was coined by
T.H. Morgan
T. Bover
G. Mendel
W. sutton
A.
T.H. Morgan
The term linkage was coined by TH Morgan. He carried out several dihybrid crosses in Drosophila to study genes that were sex-linked. He described the physical association of genes on a chromosome.
In the following human pedigree, the filled symbols represent the affected individuals. Identify the type of given pedigree. 
Autosomal dominant
X-linked recessive
Autosomal recessive
X-linked dominant
B.
X-linked recessive
The given pedigree shows the autosomal recessive disorder. In this disorder, the individual inherit two mutated genes, one from each parent. This disorder is usually passed on by two carriers. Health is rarely affected, but individual have one mutated gene(recessive gene) and one normal gene(dominant gene) for the condition. The carriers have a 25% chance of having an unaffected child with normal genes, 50% chance of having an unaffected child who also is a carrier and a 25% chance of having an affected chid with recessive genes.
A colour blind man marries a woman with normal sight who has no history of colour blindness in her family. What is the probability of their grandson being colour blind?
0.5
1
Nil
0.25
C.
Nil
When a colour blind (XCY) marries to a woman with normal sight (XX) who has no family history of colour blindness, all of their sons will be normal pure and all of their daughters will be carriers as shown below:
So in the next generation, the children of all of their son will be normal in all conditions(except the case in which the wife involved is not carrier neither colour blind). For carrier daughters.
(i) If they many to a normal man 50% of their grandsons will become colour blind as
(ii) If carrier daughter marries to a colour blind man 50% of their grandson will be colour blind along with 50% of the grand daughter while rest 50% of the grand daughters will be carriers as
So in both the above cases, the result shows 50% of grand sons will be colour blind which in terms of over all progress (son + daughter) comes as 25% thus confirming the probability as 0.25.
In his classic experiments on pea plants, Mendel did not use
Seed colour
Pod length
Seed shape
Flower position
B.
Pod length
Pod length was not considered by Mendel in his experiments. For his experiments, Mendel choose seven characters of pea plants which are:
1. Seed colour
2. Seed shape
3. Flower colour
4. Pod colour
5. Pod shape
6. Flower position and
7. Plant height
Fruit colour in squash is an example of
recessive epistasis
dominant epistasis
complementary genes
inhibitory genes
B.
dominant epistasis
Fruit colour is squash is an example of eominant cpistasis in which the dominant gene(epistatic gene) masks be to hide the effect of another gene (recessive hypostic gene). Squash fruit appear white due to the epistatic effect of 'W' allele (white colour) over 'G' allele (green colour)
A normal-visioned man whose father was colour-blind, marries a woman whose father was also colour-blind. They have their first child as a daughter. What are the chances that this child would be colour-blind?
100%
0%
25%
50%
B.
0%
Colour blindness is a X-linked disease. So, woman whose father was colourblind will be carrier for the disease.
So, possibility of a colourblind daughter (i.e., XcXc in F1 generation is 0%.)
F2 generation in a Mendelian cross showed that both genotypic and phenotypic ratios are same as 1:2:1. It represents a case of
codominance
dihybrid cross
monohybrid cross with complete dominance
monohybrid cross with incomplete dominance
D.
monohybrid cross with incomplete dominance
Monohybrid cross with incomplete dominance shows both genotypic and phenotypic ratio as same (1 : 2 : 1).
Genotypic ratio - 1(AA):2(Aa):1(aa)
Phenotypic ratio - 1(Red):2(Pink):1(White)
A human female with Turner's syndrome
has 45 chromosomes with XO
has one additional X - chromosome
exhibits male characters
is able to produce children with normal husband
A.
has 45 chromosomes with XO
Turner syndrome is a chromosomal condition that affects the development in females. The most common feature of Turner syndrome is short stature, which becomes evident by the age of about 5. An early loss of ovaries develop normally at first, but egg cells usually die prematurely and most ovarian tissue degenerates before birth. In other words, the absence of one of the X - chromosome i.e., 45 with XO (or 44 + XO).
Which one of the following is a wrong statement regarding mutations?
Deletion and insertion of base pairs cause frame-sheft mutations
Cancer cells commonly show chromosomal aberrations
UV and Gamma rays are mutagens
Change in a single base pair of DNA does not cause mutation
D.
Change in a single base pair of DNA does not cause mutation
Change in single base pair of DNA cause mutation as if mutated to termination codon or other amino acid codon-specific. Cancer is the uncontrolled process of cell division. The causal agents are certain chemicals, radiation, viruses that behave that cancer is a genetic disease caused by multiple mutation within the DNA.
A test cross is carried out to
determine the genotype of a plant at F2
predict whether two traits are linked
assess the number of alleles of a gene
determine whether two species or varieties will breed successfully
B.
predict whether two traits are linked
When F1 hybrid is crossed with its recessive parent, it is called test cross, By test cross heterozygosity and homozygosity of the organism can be tested. It gives 1:1 ratio in monohybrid and 1:1:1:1 ratio in dihybrid condition. In presence of linkage the ratio varies from this.
A man whose father was colour blind marries a woman, who had a colourblind mother and normal father. What percentage of male children of this couple will be colourblind.
25%
0%
50%
75%
C.
50%
As colour blindness is an autosomal recessive genetic disorder, for it is present at X -chromosome. Thus, according to the situation given in the question, a man whose father was colour blind (will be, i.e, XY normal) marries a woman whose mother was colour blind and father was normal (i.e, this woman will be a carrier) according to the cross given below.
Thus, when marriage will happen between a normal man and a carrier woman, in that case, percentage of a male child to be colour blind is 25% (this can be easily observed from the cross given below)
The idea of mutations was brought forth by
Hugo de Vries, who worked on evening primrose
Gregor Mendel, who worked on Pisum sativum
Hardy Weinberg, who worked on allele frequencies in a population
Charles Darwin, Who observed a wide variety of organisms during sea voyage
A.
Hugo de Vries, who worked on evening primrose
Hugo de Vries worked on evening primrose (Oenothera lamarckiana) and put forward the idea of mutation.Represented below is the inheritance pattern of a certain type of traits in humans. Which one of the following conditions could be an example of this pattern?
Phenylketonuria
Sickle cell anaemia
Haemophilia
Thalassemia
C.
Haemophilia
Colourblindness and haemophilia are two main sex-linked or X-linked recessive diseases. The gene of haemophilia goes to son from mother and to daughter from father. In this disease, the blood is fail to clot when exposed to air result in continuous bleeding and leads to death.
Multiple alleles are present
On different chromosomes
At different loci on the same chromosome
at the same locus of the chromosome
on non-sister chromatids
C.
at the same locus of the chromosome
Multiple alleles are present at the same locus of the chromosomes. A classical example of multiple alleles is found in ABO blood group system of humans. Despite the multiple alleles of any gene, an individual possess and can have only two alleles at a time.
An abnormal human baby with 'XXX' sex chromosomes was born due to
formation of abnormal sperms in the father
formation of abnormal ova in the mother
fusion of two ova and one sperm
fusion of two sperms and one ovum
B.
formation of abnormal ova in the mother
Formation of an abnormal ova usually occurs as an event during the formation of reproductive cells.
An error in cell division called non-disjunction can result in reproductive cells with additional chromosomes. Any of these cells if contributes in the genetic make up of child leads to trisomy of X-chromosome i.e. the child will have an extra X-chromosome. ZZ+ XX in mother will lead to birth of XXX genotype baby.
Alleles are
different phenotype
true breeding homozygotes
different molecular forms of a gene
heterozygotes
C.
different molecular forms of a gene
Alleles are different molecular forms of a gene, representing alternate forms of a given character.
Height of a pea plant-T for tallness and t for dwarfness.
T and t are alternate forms for given character of height.
Heterozygotes and homozygotes refers to inheritance of two different and similar travels for a character respectively.
A person with unknown blood group under ABO system has suffered much blood loss in an accident and needs an immediate blood transfusion. His one friend who has a valid certificate of his own blood type offers for blood donation without delay. What would have been the type of blood group of the donor friend?
Type AB
Type O
Type A
Type B
B.
Type O
Blood type 'O' has no any antigen but both types of antibodies 'a' and 'b'. The person with blood type 'O' is a universal donor.
Which one of the following conditions correctly describes the manner of determining the sex in the given samples?
XO type of sex chromosomes determine male sex in grasshopper
XO condition in humans as found in Turner syndrome determines female sex
Homozygous sex chromosomes (XX) produce male in Drosophila
Homozygous sex chromosomes (ZZ) determine female sex in birds
A.
XO type of sex chromosomes determine male sex in grasshopper
Grasshopper is an example of XO type of sex determination in which the males have only one X - chromosome besides the autosomes, whereas females have a pair of X - chromosomes.
Mutations can be induced with
IAA
ethylene
gamma radiations
infra red radiations
C.
gamma radiations
Gamma radiations are ionising radiation and are physical mutagens. They are used as mutagens in such materials, where the nucleus is deep-seated, e.g, seeds, stem cuttings, etc. 'Sharbati Sonora' variety of wheat has been developed by gamma radiations on 'Sonora- 64' variety (Mexican dwarf wheat variety).
peptide synthesis inside a cell takes place in
mitochondria
chromoplast
ribosomes
chloroplast
C.
ribosomes
The cellular factory responsible for synthesising proteins (peptide synthesis) is the ribosome.
Test cross in plants of in Drosophila involves crossing
Between two genotypes with recessive trait
Between two F1 hybrids
the F1 hybrid with a double recessive genotype
Between two genotypes with dominant trait
C.
the F1 hybrid with a double recessive genotype
When F1 hybrid is crossed with a recessive parent then it is called test cross. It is also a backcross. A test cross is done to test whether the dominant parent is heterozygous or homozygous.
Sweet potato is homologous to
potato
colocasia
ginger
turnip
D.
turnip
Sweet potato (Ipomoea batatas) and turnip (Brassica rapa)both are roots. However, sweet potato is tuberous adventitious root while turnip is napiform tap -root.
Which one of the following conditions of the zygotic cell would lead to the birth of a normal human female child?
Two X - chromosomes
Only one Y- chromosomes
Only one X - chromosome
One X and one Y- chromosome
A.
Two X - chromosomes
The sex determining mechanism in case of humans is XY type. Sperms are of two types, one containing X -chromosome and another containing Y- chromosome.
Which one of the following is a wrong matching of a microbe and its industrial product, while the remaining three are correct?
Yeast - statins
Acetobacter aceti - acid
Clostridium Butulicum - lactic acid
Aspergillus niger - citric acid
C.
Clostridium Butulicum - lactic acid
Clostridium butulicum forms butyric acid
Which one of the following cannot be explained on the basis of Mendel's Law of Dominance?
the discrete unit controlling a particular character is called a factor
Out of one pair of factors, one is dominant and the other recessive
Alleles do not show any blending and both the characters recover as such in F2 generation
Factors occur in pairs
C.
Alleles do not show any blending and both the characters recover as such in F2 generation
The law of dominance does not occur universally. After Mendel, several cases were recorded by scientists, where a clear deviation from the law of dominance was seen. Such a deviation may be seen in the form of Incomplete dominance or Blending inheritance Co-dominance.
Where F1 hybrids exhibited a mixture of blending or character of two parents, the case is considered as that of incomplete dominance blending inheritance. It simply means that two genes of an allelomorphic pair are not related as dominant or recessive, but each of them expresses itself partially. In the case of 4 o' clock plant, when plants with red flowers are crossed with plants having white flowers are crossed with plants having a white flower, the F1 hybrids bear a pink flower. When these pink flowers are self-pollinated, they develop red, pink and white flowers in the ratio of 1: 2:1 respectively.
The genotype of plant showing the dominant phenotype can be determined by
test cross
dihybrid cross
pedigree analysis
back cross
A.
test cross
In Genetics, a test cross, first introduced by Gregor Mendel, is used to determine if an individual exhibiting a dominant trait is homozygous or heterozygous for that trait. More simply, test cross determines the genotype of an individual with a dominant phenotype. In some sources, the test cross is defined as being a type of back cross between the recessive homozygote and F1 generation
Select the correct statement from the ones given below with respect to dihybrid cross.
Tightly linked genes on the same chromosome show higher recombinations
Genes far apart on the same chromosome show very few recombinations
Genes loosely linked on the same chromosome show similar recombinations as the tightly linked ones.
Tightly linked genes on the same chromosome show very few recombinations
D.
Tightly linked genes on the same chromosome show very few recombinations
Recombination is a rearrangement of genes during meiosis so that a gamete contains a haploid genotype with a new a gene combination. Morgan and his group found that when genes were grouped on the same chromosome, some genes were very tightly linked (showed very low recombination), while other were loosely linked (showed higher recombination).
Which one of the following symbols and its representation, used in human pedigree analysis is correct?
= Mating between relatives
= unaffected male
= Unaffected female
= Male affected
A.
= Mating between relatives
= Mating between relatives
= unaffected female
= Unaffected male
= Unspecified SexWhich one of the following statements about the particular entity is true?
Centromere is found in animal cell which produces ester during cell divison
the gene for producing insulin is present in every body cell
Nucleosome is formed of nucleotides
DNA consists of a core of eight histones
C.
Nucleosome is formed of nucleotides
A scientist has analysed the human DNA sequence present in a human -mouse somatic cell hybrid line possessing a translocation involving human chromosome-II and X. This data indicates that the human insulin gene is located on the short arm of chromosome-II in everybody cell but is not expressed in all cells.
In genetic engineering, a DNA segment (gene) of interest, is transferred to the host cell through a vector. Consider the following four agents (A-D) in the regard and select the correct option about which one or more of these can be used as a vector/vectors
A) A bacterium
B) Plasmid
C) Plasmodium
D) Bacteriophage
A, B and D only
A only
A and C only
B and D only
D.
B and D only
Plasmids are the extrachromosomal DNA found in bacterial cells. These are commonly used as vectors in genetic engineering programmes because these have the capacity of binding with eukaryotic DNA.
A bacteriophage is a virus that is parasitic within a bacterium. These also, are the important tools in genetic engineering as cloning vectors.
The fruit fly, Drosophila melanogaster was found to be very suitable for experimental verification of chromosomal theory of inheritance by Morgan and his colleagues because
It reproduces parthenogenetically
a single mating produces two young files
smaller female is easily recognisable from larger male
it completes life cycles life cycle in about two weeks
D.
it completes life cycles life cycle in about two weeks
The fruit fly, Drosophila melanogaster was found to be very suitable for experimental verification of chromosomal theory of inheritance by Morgan and his colleagues because
* It completes its life cycle in a very short period (ie, about two weeks).
* a single mating produces many offsprings.
* larger female is easily recognisable from the smaller male.
Study the pedigree chart of a certain family given below and select the correct conclusion which can be drawn for the character.
The female parent is heterozygous
The parents could not have a had a normal daughter for this character
The trait under study could not be colour blindness
The male parent is homozygous dominant
A.
The female parent is heterozygous
The given pedigree chart shows that both the daughters received the gene from the parents, while son may be normal or affected. It shows that the female parent is heterozygous.
The bacterium Bacillus thuringiensis is widely used in contemporary biology as a/an
Indicator of water pollution
insecticide
agent for the production of dairy products
the source of industrial enzyme
B.
insecticide
Bacillus thuringiensis is Gram-positive, soil dwelling bacterium also occurs naturally in the gut of caterpillars of various types of moths and butterflies.
During sporulation, B. thuringiensis forms crystals of proteinaceous insecticidal
Point mutation involves
insertion
change in the single base pair
duplication
deletion
B.
change in the single base pair
The point mutations involve alterations in the structure of gene by altering the structure of DNA. Point mutations are of two types- (i) base pair substitution and (ii) Frameshift substitution.
Insertion is the addition of one of more nitrogenous bases to a nucleotide chain.
Duplication is the presence of one block of genes more than once in the haploid component.
Deletion is the removal of one or more nitrogenous bases from a nucleotide chain.
Which one of the following is commonly used in the transfer of foreign DNA into crops plants?
Trichoderma hazianum
Meloidogyne incognita
Agrobacterium tumefaciens
Penicillium expansum
C.
Agrobacterium tumefaciens
The uptake of foreign DNA or transgenes by plant cells is called transformation. A variety of techniques have been used to introduce transgenes into plant cells, these can be grouped into the following two categories0 (i) Agrobacterium-mediated and (ii) direct gene transfers.
Agrobacterium tumefaciens mediated transformation eliminates the need for regeneration from tissue explants.
Which one of the following condition in humans is correctly matched with tis chromosomal abnormality /linkage?
Klinefelter's syndrom-44 autosomes + XXX
Colourblindness- Y-linked
Erythroblastosis foetails - X-linked
Down syndrome - 44 autosomes + XO
A.
Klinefelter's syndrom-44 autosomes + XXX
Klinefelter's syndrome si represented by 44 autosome+ XXY. When an abnormal egg with XX chromosome is fertilised by a sperm carrying Y-chromosome a zygote having XXY sex chromosomes is formed. The resulting young one is an abnormal sterile male.
Haploids are more suitable for mutation studies than the diploids. This is because
Haploids are reproductively more stable than diploids
mutagens penetrate in haploids more effectively than is diploids
haploids are more abundant in nature than diploids
all mutations, whether dominant or recessive are expressed in haploids
D.
all mutations, whether dominant or recessive are expressed in haploids
Haploid plants can be produced in large number by anther and ovary cultures. Haploids may be useful for isolation of mutants, since, even recessive mutant alleles will be expressed in the mutagen treated generation itself. Desirable mutants may be selected at the haploid level and their chromosome number may be doubled to obtain homozygous mutant lines in a single generation.
Inheritance of skin colour in humans is an example of
chromosomal aberration
point mutation
polygenic inheritance
codominance
C.
polygenic inheritance
Inheritance of skin colour in humans is the result of polygenic inheritance or multiple factor inheritance. The inheritance of human skin colour was studied by C.B. Davenport in 1913.
Two genes R and Y are located very close on the chromosomal linkage map of a maize plant. When RRYY and rryy genotypes are hybridised, the F2 segregation will show:
higher number of the recombinant types.
segregation in the expected 9 : 3 : 3 : 1 ratio
segregation in 3 : 1 ratio
higher number of the parental types.
D.
higher number of the parental types.
Law of independent assortment does not applicable when the gene of different character occupy on the same homologous chromosome i.e., linked gene.
A common test to find the genotype of a hybrid is by
crossing of one F2 progeny with male parent
crossing of one F2 progeny with female parent
studying the sexual behaviour of F1 progenies
crossing of one F1 progeny with male parent
D.
crossing of one F1 progeny with male parent
Test cross, crossing of F1 progeny to the recessive parent is used to find the genotype of the progeny.
Which one of the following is the most suitable, medium for culture of Drosophila melanogaster?
Moist bread
Agar agar
Ripe banana
Cow dung
C.
Ripe banana
Drosophila melanogaster is commonly called as fruitfly and is often used in genetic and developmental biology researchers. The ripe banana is the most suitable medium for the culture of this fly.
Moist bread is a culture medium for the fungus Rhizopus while agar-agar is used as a tissue culture medium.
Phenotype of an organism is the result of
mutations and linkages
cytoplasmic effects and nutrition
environmental changes and sexual dimorphism
genotype and environment interactions
C.
environmental changes and sexual dimorphism
Phenotype is the observable characteristics or the total appearance of an organism. It is determined by its genes, the dominance relationships between the alleles and by the interaction during development between its genetic constitution (genotype) and the environment.
Mutation leads to variation and linkage to store genatype. Cytoplasmic effect a nutrition generally do not determine the phenatype.
Which one of the following is an example of polygenic inheritance?
Flower colour in Mirabilis jalapa
Production of male honey bee
Pod shape in garden pea
Skin colour in humans
D.
Skin colour in humans
Polygenic inheritance involves the determination of a particular phenotypic characterisitc by many genes, called polygenes (i.e., the group of genes influencing a quantitative characteristic), each having a small effect individually.
The characteristics controlled in this way show continuous variation and are called polygenic characters e.g., height and skin colour in humans.
The polygenic inheritance is called multifactorial inheritance or quantitative inheritance.
The pink flower colour in Mirabilis jalapa is an example of incomplete dominance while production of male honey bee is an example of parthenogenesis.
One gene – one enzyme hypothesis was postulated by
R. Franklin
Hershey and Chase
A. Garrod
Beadle and Tatum
D.
Beadle and Tatum
'One gene - one enzyme' hypothesis was given by Beadle and Tatum (1948) which states that particular gene controls the synthesis of specific enzyme. Later, it was modified to 'one gene-one polypeptide hypothesis' by Yanofsky et.al. (1965).
Test cross involves
crossing between two genotypes with recessive trait
crossing between two F1 hybrids
crossing the F1 hybrid with a double recessive genotype
crossing between two genotypes with dominant trait
C.
crossing the F1 hybrid with a double recessive genotype
The test cross involves the crossing of F1 hybrid with a double recessive genotypic parent. By test cross, the heterozygocity and homozygocity of the organism can be tested.
Thus, the offspring will be 100% dominant, if the individual which crossed with recessive parent i.e., (tt) was homozygous dominant and ratio will be 50% dominant and 50% recessive if the individual was heterozygous dominant. In dihybrid test cross, ratio will be 1:1:1:1.
Sickle cell anaemia has not been eliminated from the African population because
it is controlled by recessive genes
it is not a fatal disease
it provides immunity against malaria
it is controlled by dominant genes
C.
it provides immunity against malaria
Sickle cell anaemia (in which RBCs become sickle shaped and stiff) is a genetic disorder that is autosomal and linked to a recessive allele. It has not been eliminated from the african population because it provides immunity against malaria. People who are heterozygous for sickle allele are much less susceptible for falciparum malaria which is one of the main causes of illness and death in them. Thus, the sickle cell allele is maintained at high levels in population where falciparum malaria is common.
Both sickle cell anaemia and Huntington's chorea are
bacteria-related diseases
congenital disorders
pollutant-induced disorders
virus-related diseases
B.
congenital disorders
Both sickle cell anaemia and Huntington's chorea are congenital genetic disorders. Sickle cell anaemia was first opened by James Herrick (1904). In this disease the patient's haemoglobin level reduced to half of the normal and the RBCs become sickle shaped. A single mutation in a gene can cause sickle cell anaemia.
Huntington's chorea is caused by autosomal mutation which is dominant. The gene is present on chromosome number 4.
Among the following characters, which one was not considered by Mendel in his experiments on pea?
Stem – Tall or Dwarf
Trichomes – Glandular or non-glandular
Seed – Green or Yellow
Pod – Inflated or Constricted
B.
Trichomes – Glandular or non-glandular
During his experiments Mendel studied seven characters. Nature of trichomes i.e., glandular or non-glandular was not considered by Mendel.
Which of the following characteristics represent ‘Inheritance of blood groups’ in humans?
a. Dominance
b. Co-dominance
c. Multiple allele
d. Incomplete dominance
e. Polygenic inheritance
b, c and e
a, b and c
a, c and e
b, d and e
B.
a, b and c
IAIO, IBIO - Dominant–recessive relationship
IAIB - Codominance
IA, IB & IO - 3- different allelic forms of a gene(multiple allelism)
Select the correct match
Alec Jeffreys - Streptococcus pneumoniae
Alfred Hershey and Martha Chase - TMV
Francois Jacob and Jacques Monod - Lac operon
Matthew Meselson and F. Stah - Pisum sativum
C.
Francois Jacob and Jacques Monod - Lac operon
Francois Jacob and Jacque Monod proposed the model of gene regulation known as operon model/lac operon
– Alec Jeffreys – DNA fingerprinting technique.
– Matthew Meselson and F. Stahl – Semiconservative DNA replication in E. coli.
– Alfred Hershey and Martha Chase – Proved DNA as genetic material, not protein.
Select the correct statement
Franklin Stahl coined the term ‘‘linkage’’
Punnett square was developed by a British scientist
Transduction was discovered by S. Altman
Spliceosomes take part in translation
B.
Punnett square was developed by a British scientist
Punnett square was developed by a British geneticist, Reginald C. Punnett.
– Franklin Stahl proved semi-conservative mode of replication.
– Transduction was discovered by Zinder and Lederberg.
– Spliceosome formation is part of posttranscriptional change in Eukaryotes.
One of the breeding techniques useful to eliminate harmful recessive genes by selection is
Artificial insemination
Outbreeding
Inbreeding
MOET
C.
Inbreeding
When breeding is done between animals of the same breed for 4-6 generations, it is called inbreeding. Inbreeding is necessary if we want to develop a pure line of any animal. It exposes harmful recessive genes that are eliminated by selection. It also helps the accumulation of superior genes and the elimination of less desirable genes.
Minisatellites or VNTR's are used in
DNA fingerprinting
Polymerase chain reaction, (PCR)
gene therapy
Gene mapping
A.
DNA fingerprinting
Minisatellites or a Variable number of Tandem Repeats (VNTR) are used in DNA fingerprinting technique. In VNTR, satellite DNA acts as a probe, that shows a very high degree of polymorphism.
In the lac operon model, lactose molecules function is
inducers,which bind with the operator gene
Repressors, which bind the the operator gene
inducers, which bind the repressor protein
corepressore, which bind with the repressor protein
C.
inducers, which bind the repressor protein
Lactose or lac operon of E.coil is an example of inducible operon. Lactose is known to be inducer and substrate for the enzyme beta-galactosidase.
The thermostable enzymes, Taq and Pfu, isolated from thermophilic bacteria are
RNA polymerases
DNA ligases
DNA polymerases
Restriction endonucleases
C.
DNA polymerases
'Taq' and 'Pfu' are thermostable enzyme, which re-isolated from thermophilic bacteria.
The largest gene in man is
Insulin gene
Tumour suppressor gene
Beta globin gene of haemoglobin
Dystrophin
D.
Dystrophin
The largest known gene in human is the dystrophin gene, which has 79 axons spanning at least 2300 kb. The human dystrophin gene requires 16 hours to be transcribed.
Herbicide-resistant gene in a plant is
Mt
Gt
Ct
Bt
D.
Bt
Herbicide-resistant gene in plants is Bt gene Bacillus thuringiensis is the bacterium that occurs naturally in soil. It is now used as herbicide or biopesticide.
Which has an additional X-chromosome?
Turner’s syndrome
Klinefelter’s syndrome
Super female
Down’s syndrome
D.
Down’s syndrome
Klinefelter's syndrome is caused by one or more extra X-chromosome ( i.e., XXY, XXXY). The man with such a syndrome is sterile, has small testes, long legs and feminine characters like breasts.
Polyploidy can be induced by the application of
Auxin
Kinetin
Colchicine
Ethylene
C.
Colchicine
Colchicine is a poisonous chemical, isolated from seeds and bulbs of autumn crocus (Colchicum autumnale). It blocks spindle formation and thus, inhibits the movement of sister chromatids to the opposite poles. The resulting restitution nucleus includes all the chromatids. As a result, the chromosome number of the cell is doubled, which leads to polyploidy.
A fern differs from a moss in having
Swimming archegonia
Swimming antherozoids
Independent gametophytes
Independent sporophytes
D.
Independent sporophytes
Fern (pteridophyte) differs from a moss s(bryophyte) in having independent gametophyte, while in moss the sporophyte is simpler than the gametophyte and remains attached to the parent gametophyte throughout its life. This sporophyte is dependent upon gametophyte partially or wholly for its nutrition.
Development of an embryo without fertilization is called as
Apomixis
Polyembryony
Parthenocarpy
Parthenogenesis
D.
Parthenogenesis
Parthenogenesis (virgin origin) is the development of an embryo from an unfertilized egg or if a spermatozoan does penetrate the egg, there is no union of male and female pronuclei. It is found in many plants (dandelions and hawk weeds) and (aphids and honey bees).
Chromosomes are arranged along the equator during
Prophase
Metaphase
Anaphase
Telophase
D.
Telophase
In plant cells, during metaphase chromosomes line up around the equator of the spindle and attached by their centromere to the spindle fibres (microtubules). In animal cells, during metaphase, smaller chromosomes are usually central in position with larger ones peripheral in position.
Phage genome site on bacterial chromosome resulted in the structure
Nucleic acid
Heterocyst
Prophage
None of these
C.
Prophage
Prophage is the DNA of bacteriophage that is repressed for lytic functions and is maintained in the host bacterium in a stable state. Te phage genome is integrated into DNA of its bacterial host and may be replicated along with the host DNA, as in the case or bacteriophage lambda or may be maintained as extrachromosomal DNA, as in the case for bacteriophage, lambda P1
The mobile genetic element is
Transposon
Mutation
Endonuclease
Variation
A.
Transposon
The mobile genetic element is broadly any genetic element capable of moving itself with or without duplication from one site in a genome to another.
Given below is a sample of portion of DNA strand given the base sequence on the opposite strand. What is so special show in it?
5’−GAATTC….3’
3’−CTTAAG … 5’
Detection mutation
Start codon at 5′ end
The palindromic sequence of base pairs
Replication completed
C.
The palindromic sequence of base pairs
Palindromic DNA is base sequence of DNA which reads the same forward and backwards. It has a similar sequence in both the strands. Different types of palindromic sequences are recognised by restriction endonucleases.
A point mutation where guanine is replaced by cytosine is also called
Frameshift mutation
Transition mutation
Translocation mutation
Transversion mutation
D.
Transversion mutation
The base pair mutations are the most common type of mutations. These can be further categorised into two types
(a) Transitions, i.e. in which a purine base is replaced by another purine and pyrimidine is replaced by
another pyrimidine.
(b) Transversion, ie those in which a purine (guanine) is replaced by a pyrimidine (cytosine) and vice-versa.
In animals normally which organism has a maximum number of chromosomes?
Butterfly
Elephant
Hermit crab
Chimpanzee
A.
Butterfly
Butterflies have most numbers of a chromosome in animal kingdom about 380.
During meiosis-I, the bivalent chromosomes clearly appear as tetrads during
Diakinesis
Diplotene
Pachytene
Zygotene
C.
Pachytene
During meiosis-l, in pachytene phase of prophase-l, the bivalent chromosomes clearly appear as tetrads for crossing over.
Snapdragon flower is an exception of Mendel’s laws. It is a good example of
Law of dominance
Complementary gene
Codominance
Incomplete dominance
D.
Incomplete dominance
4 O'clock and snapdragon flower are the best examples of incomplete dominance wherein heterozygous condition pink flowers are produced from white and red parents. It is an exception to Mendel's law of dominance.
Number of Barr body which will found in case of Turner’s syndrome will be
1
2
0
Can't be determined by given data
C.
0
The number of barr body in human = one less than the number of x Chromosome. In case of Turner syndrome 45(44+ X) chromosomes are found. So number of Barr bodies will be-zero.
What base is responsible for hot spots for spontaneous pint mutations?
Adenine
Guanine
5-bromouracil
5-methyl cytosine
C.
5-bromouracil
Hotspots in any region in a gene that mutates at very high frequency than the neighbouring regions of the gene.
In peal plants, yellow seeds are dominant to green. If a heterozygous yellow seeded plant is crossed with a green seeded plant, what ratio of yellow and green seeded plants could you expect in F1-generation
9 : 1
1 : 3
3 : 1
50 : 50
D.
50 : 50
Yellow seeds are dominant is green (Y), os, a heterozygous yellow seeded plant will have a genotype of (Y,y). when these plants are crossed, the F1 generation will have the ratio of yellow; green as 50:50.
In a mutational event, when adenine is replaced by guanine, it is a case of
Frameshift mutation
Transcription
Transition
Transversion
C.
Transition
Transition is substitution gene mutation in which a purine (adenine) is replaced by another purine (guanine) or a pyrimidine (thymine) is replaced by another pyrimidine cvytosine). Change of codon ATC to GTC or ATT or ACC is an example of transition.
Transversion in substitution gene mutation in which a purine (A or G) is replaced by a pyrimidine (T or C) or vice versa.
Match the following Column I with Column II.
| Column I | Column II |
| A. Complementrary Ratio | 1. 9:7 |
| B. Supplementary Ratio | 2. 9:3:4 |
| C. Epistatic Ratio | 3. 12:3:1 |
| D. Inhibitory Ratio | 4. 13:3 |
A-4, B-1, C-3, D-2
A-1, B-2, C-3, D-4
A-4, B-1, C-2, D-3
A-1, B-3, C-2, D-4
B.
A-1, B-2, C-3, D-4
Epistasis is an interaction between two or more genes to control a single phenotype. Dominant epistasis also called masking has a ratio 12:3:1 in the F2 phenotype supplementary genes which is recessive epistasis has ratio 9:3:4
Complementary gene where both dominant alleles are needed for phenotype has ratio 9:7. Inhibitor gene where one gene inhibits is an expression of another gene has ratio 13:3 in F2 progeny.
A woman with two genes (one on each X-chromosome) for haemophilia and one gene for colour blindness on the X-chromosome marries a normal man. How will the progeny be?
All sons and daughters are haemophilic and colourblind
Haemophilic and colourblind daughters
50% haemophilic colourblind sons and 50% haemophilic sons
50% haemophilic daughters and 50% colourblind daughters
C.
50% haemophilic colourblind sons and 50% haemophilic sons
Haemophilia and colour blindness both are recessive X-linked traits. They express in males when present in single copy (heterozygous) but in females, they express only when present in homozygous condition.
A hereditary disease which is never passed on from father to son is
X-chromosomal linked disease
Autosomal linked disease
Y chromosomal linked disease
None of the above
A.
X-chromosomal linked disease
Man has only one X-chromosome that is inherited to his daughter. Therefore, a hereditary disease, which is X-chromosomal linked, is never passed on from father to son.
A man of blood group- A marries a woman of blood group- AB, which type of progeny would indicate that man is heterozygous?
O
B
A
AB
B.
B
In this case, progeny with blood group- B is produced only when man is heterozygous, ie, IAIO.
In Pisum sativum, there are 14 chromosomes. How many types of homologous pairs can be prepared?
14
7
214
210
A.
14
Pisum sativum is a angiospermic plant. In angiosperms diploid chromosomes are present, that is, plant body belongs to sporophytic generation (2n).
In Pisum sativum, 2n=14
Therefore, there are 7 types of homologous pairs in Pisum sativum.
Pure tall plants are crossed with pure dwarf plants. In the F1 generation, all plants were tall. These tall plants of F1 generation were selfed and the ratio of tall to dwarf plants obtained was 3 : 1. This is called
dominance
inheritance
codominance
heredity
A.
dominance
Law of Dominance states that, in a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation.
Eg. When pure tall plant is crossed with pure dwarf plant. In F1 generation, all plants obtained were tall. When these tall plants were selfed, ratio of tall to dwarf plants obtained was 3 : 1.
Therefore, allele of tallness is dominant to allele of dwarfness.
Chromosome complement with 2n - 1 is called
monosomy
nullisomy
trisomy
tetrasomy
A.
monosomy
Aneuploidy is defined as addition or removal of one or few chromosmes.
(i) Monosomy is (2n - 1), eg, Turner's syndrome
(ii) Nullisomy is (2n - 2)
(iii) Trisomy is (2n +1), eg, Klinefelter's syndrome
(iv) Tetrasomy is (2n + 2).
The trisomy for 21st chromosome is called
Down's syndrome
Turner's syndrome
Sickle cell anaemia
Klinfelter's syndrome
A.
Down's syndrome
| Abnormality | Cause | Characteristic |
| Down's Syndrome | Trisomy of 21st chromosome (45 A + XX/ XY) | Mental retardation, prominent head, flattened nasal bridge, open mouth, short stature etc |
| Turner's Syndrome | Non- disjunction of sex chromosome (2n = 45; 44A +XO) | Sterile female, webbed neck, no breast development, no menstruation or egg production |
| Klinefelter's Syndrome | Non- disjunction of sex chromosomes (2n = 47; 44A + XXY) | Sterile male with low IQ, testes underdeveloped. |
| Sickle cell anaemia | Molecular gene mutation of gene HbA | Sickle shaped RBCs, do not transport O2 efficiently |
Chromosome complement with 2n - 1 is called
monosomy
nullisomy
trisomy
tetrasomy
A.
monosomy
Aneuploidy is a change in the chromosme number that does not involve entire sets of chromosome. It can be of following types:
(i) Monosomic (2n - 1)
(ii) Trisomic (2n +1)
(iii) Nullisomic (2n - 2)
(iv) Tetrasomic (2n + 2)
(v) Double monosomic (2n - 1 - 1)
(vi) Doble trisomic (2n + 1 + 1)
L- shaped chromosomes are also called
acrocentric
telocentric
sub- metacentric
None of these
C.
sub- metacentric
The shape of chromosome is determined by the position of centromere on the chromosomes. They may be of following five types:
(i) Acentric- centromere is absent.
(ii) Telocentric- centromere present at one end of chromosome.
(iii) Acrocentric- when chromosome is divided into a very small segment at one end and a very large segment on the other end.
(iv)Submetacentric- when chromosome has two unequal segments and forms V- shaped structure.
(v) Metacentric- two equal segments of chromosomes
If root of a flowering plant has 24 chromosomes, then its gamete has how many chromosomes?
24
12
4
8
B.
12
The root cell of flowering plant is diploid (2n = 24) while the gamete is haploid, therefore, the number of chromosomes becomes 12 in the gamete.
The cells of stem, leaf and somatic cells of flower are diploid, therefore, they contain the chromosome number 2n = 24.
Balbiani rings are the structural features of
allosomes
polytene chromosomes
autosomes
Lampbrush chromosomes
B.
polytene chromosomes
Balbiani rings are large RNA puffs reported in the salivary gland chromosomes (polytene chromosome) of Chironomus insect during larval development.
X- linked recessive gene is
always expressed in male
always expressed in femlae
lethal
sub- lethal
A.
always expressed in male
X- linked genes are represented twice in female and once in male. The recessive X- linked genes have characteritic criss- cross inheritance, ie, male transmits his X- linked recessive genes to his grandson through his daughter.
Which of the following is a test cross?
Tt tt
TT tt
Tt Tt
tt tt
A.
Tt tt
A test cross is a cross between heterozygous F1 hybrid and double recessive homozygous eg, Tt tt to show whether F1 is homozygous or heterozygous.
1 : 2 : 1 phenotypic and genotypic ratio is found in
complementary genes
blending inheritance
multiple alleles
pseudo alleles
B.
blending inheritance
Incomplete dominace or blending inheritance was first seen in Mirabilis jalapa (4' O Clock plant). Here, when red flowers are crossed with white variety, the F1 hybrid is pink and F2 ratio is 1 red : 2 pink : 1 white.
RR : Rr : Rr : rr
1 : 2 : 1 - Genotypic and Phenotypic ratio
A man and a woman, who do not show any apparent signs of a certain inherited disease, have seven children (2 daughters and 5 sons). Three of the sons suffer from the given disease but none of the daughters are affected. Which of the following mode of inheritance do you suggest for this disease?
Autosomal dominant
Sex-linked dominant
Sex-limited recessive
Sex-linked recessive
D.
Sex-linked recessive
Sex linked characteristic is determined by the genes located on the sex chromosome ie X or Y. Sex limited characteristic is the condition where expression of sex linked genes is limited to one sex.
In the given problem, neither man nor woman are deceased by the disease. Therefore, women must be the carrier of the disease causing gene. Also, none of the daughters are suffereing from the disease except the sons, ie, daughters are also carrier.
Suppose, XY = genotype of man
XdX = genotype of woman (d refers to disease causing gene)
The probability for each combination is 25%. Therefore, among seven children, 2 are normal daughter, 3 diseased sons and 2 normal sons are possible.
A haemophilic woman marries a normal man then
all the children will be normal
all the sons will be haemophilic
all the girls will be haemophilic
half girls will be haemophilic
B.
all the sons will be haemophilic
Haemophilia is x linked recessive trait (where females are the carrier) in which a person lacks certain clotting factors which don't let the blood to clot properly. 
A woman with normal vision, but whose father was colourblind, marries a colourblind man. Suppose that the fourth child of this couple was a boy. This boy
must have normal colour vision
will be partially colourblind since he is heterozygous for the colourblind mutant allele
must be colourblind
may be colourblind or may be of normal vision
D.
may be colourblind or may be of normal vision
Colourblindness is a sex linked disorder (X- linked). It is always transferred from mother to son.
In the mentioned question, woman whose father was colourblind, will be the carrier of the colourblind trait. If this woman marries a colourblind man, following possibilities are possible-
(i) If woman is Normal-
(ii) If woman is Carrier-
Hence, in both the cases, boy may be colourblind or may be of normal vision.
Husband has blood group A and wife has blood group B. What is the blood group of children
A
B
AB
A, B, AB or 0
D.
A, B, AB or 0
Thus, if husband has blood group A and wife has blood group B, the blood group of children may be A, B, AB or 0
Which of the following is not a hereditary disease?
Cretinism
Cystic fibrosis
Thalassaemia
Haemophilia
A.
Cretinism
Cretinism is a disorder which is caused by the deficiency of thyroid hormones in infants. Symptoms of this disorder-
This disease can be treated by an early administration of thyroid hormones.
de Vries gave his mutation theory on organic evolution while working on
Althea rosea
Drosophila melanogaster
Oenothera lamarckiana
Pisum sativum
C.
Oenothera lamarckiana
Hugo de Vries (1848-1935) proposed mutation theory for the formation of new species. According to him, new species are not formed by continuous variations but by sudden appearance of variations which he named as mutations. He stated that these mutations are heritable and persist in successive generations. For proposing this theory he performed experiments on Oenothera lamarckiana (evening primrose).
A woman with 47 chromosomes due to three copies of chromosome 21 is characterized by
Down syndrome
triploidy
Turner syndrome
super femaleness
A.
Down syndrome
Down syndrome is caused by the trisomy on 21st chromosome. In this, fusion of normal n gamete (haploid) takes place with n + 1 gamete (diploid). It was first described by J. Langdon Down in 1866.
Common symptoms include short height, stocky build, short hands, flattened facial features and poor muscle tone and are mentally retarded.
Using imprints from a plate with complete medium and carrying bacterial colonies, you can select streptomycin resistant mutants and prove that such mutations do not originate as adaptation. These imprints need to be used
only on plates with streptomycin
on plates with minimal medium
only on plates without streptomycin
on plates with and without streptomycin
A.
only on plates with streptomycin
Plates having streptomycin allow to propagate only those bacteria, which are resistant to the antibiotic.
In order to find out the different types of gametes produced by a pea plant having the genotype AaBb, it should be crossed to a plant with the genotype
aaBB
AaBb
AABB
aabb
D.
aabb
Scientists perform test cross to find out the different types of gametes or the genotype of an unknown individual. Test cross is performed always between the F heterozygous plants and pure recessive (homozygous) parent plant. So, in the given case AaBb should be crossed with aabb.
Which one of the following can help in the diagnosis of a genetical disorder?
ELISA
ABO blood group
PCR
NMR
C.
PCR
PCR is a technique in which a small fragment of DNA is rapidly cloned or duplicated to produce multiple DNA copies. Thus, it helps in the diagnosis of a genetical disorder. This technique was conceived by American biochemist Kary B. Mullis.
The children of a haemophilic man and a normal woman are
all haemophilic
only daughters are haemophilic
only sons are haemophilic
neither sons nor daughters are haemophilic
D.
neither sons nor daughters are haemophilic
The children of a haemophilic man and normal woman will be all normal. Neither sons nor daughters (only carrier) will be haemophilic.
If a plant having yellow or round seeds was crossed with another plant having green and wrinkled seeds then F, progeny are in the ratio
15 : 1
1 : 15
1 : 13
all yellow and round seeds
D.
all yellow and round seeds
Mendel crossed a dominant homozygous yellow, round seeded plant with a recessive homozygous green and wrinkled seeded plant. The F1 offsprings produced are heterozygous yellow, round seeded plants.
A man of blood group 'A', marries a woman of blood group 'B', both of them are heterozygous for blood group, chances of their first child having blood group AB will be
25%
50%
75%
100%
A.
25%
Man Blood group Women Blood group
There is 25% chances of first offspring having blood group AB.
2n-1 condition represent
tetrasomy
trisomy
monosomy
multisomy
C.
monosomy
When changes involve only a few chromosome say one or two and not the entire genome, the phenomenon is called aneuploidy. Monosomy is a case of aneuploidy, when there is loss of one chromosome from a pair of homologue.
2n - 1 condition is called
trisomy
monosomy
nullisomy
tetrasomy
B.
monosomy
2n - 1 condition represents diploid set of chromosomes having loss of one chromosome, the presence of one unpaired chromosomes along with diploid set is called monosomy.
Trisomy is a chromosomal disorder characterized by an additional chromosome. Eg. Down syndrome.
Nullisomy is a genetic condition involving the lack of both the normal chromosomal pairs for a species. This condition is represented by 2n - 2.
Tetrasomy is a form of aneuploidy with the presence of four copies, instead of normal two, of particular chromosomes.
When paternal and maternal chromosomes change their materials with each other in cell division this event is called
synapsis
crossing over
bivalent forming
dyad- forming
B.
crossing over
Crossing over is the mutual exchange of segments of homologous chromatids during first meiotic prophase.
Synapsis is the fusion of chromosome pairs at the start of meiosis.
DNA replication precedes the start of Meiosis I. During Prophase I, homologous chromosomes pair and form synapses. The paired chromosomes are called bivalents and the formation of chiasmata caused by genetic recombination becomes apparent.
Dyad formation is a double chromosome resulting from the splitting of a tetrad during meiosis (germ cell formation).
Which of the following conditions represents a case of codominant genes
A gene expresses itself, suppressing the phenotypic effect of its alleles.
Genes that are similar in phenotypic effect when present separately, but when together interact to produce a different trait.
Alleles, both of which interact to produce a trait, which may or may not resemble either of the parental types.
Alleles, each of which produces an independent effect in a heterozygous condition.
D.
Alleles, each of which produces an independent effect in a heterozygous condition.
Codominance is the phenomenon when the two alleles of a gene neither show dominant recessive relationship nor show intermediate condition, but both of them express themselves independently in heterozygous condition. This has been reported in roan coat colour of cattle (i.e., patches of two different colours on the skin).
Assertion: XX-XY type of sex determination mechanism is an example of female heterogamety and is found in Drosophila.
Reason: Male heterogamety is seen in moths where males produce two different types of gamete.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
D.
If both assertion and reason are false.
Chromosomal determination of sex is based on heterogamety or occurrence of two types of gamete in one of the two sexes. In Drosophila XX-XY type of sex determination is found where males are heterogametic. In moths, ZO-ZZ type of sex determination occur where males are homogametic.
If both parents are carriers for thalassaemia, which is an autosomal recessive disorder, what are the chances of pregnancy resulting in an affected child?
25%
100%
No chance
50%
A.
25%
Thalassaemia is an autosomal recessive disorder.
In the given case, both the partners are carriers for thalassaemia i.e., are heterozygous. Persons homozygous for thalassaemia suffer from severe haemolytic anaemia. Heterozygous persons are also not normal, but show the defect in a less severe form (thalassaemia minor). The probability of their progeny being affected with the disease i.e., with homozygous genotype is 25% only as shown below:
Parents : Tt Tt
Offspring: TT : Tt : tt
1 : 2 : 1
Normal- TT (25%)
Carriers- Tt (50%)
Affected- tt (25%)
In rabbits, the gene for grey fur (G) is dominant over that for black fur (g). In a litter, if 50% rabbits are grey, then the possible parental cross combination is
GG x Gg
gg X gg
GG x GG
Gg x gg
D.
Gg x gg
When heterozygous grey individuals (Gg) are crossed with homozygous black individuals (gg), then grey and black individuals will be obtained in equal ratio. It is a type of test cross and can be illustrated as:
Barr body is missing in the female suffering from
Huntington's disease
Tay-sach's disease
Klinefelter's syndrome
Turner's syndrome.
D.
Turner's syndrome.
In normal females, number of Barr bodies is one less than the number ofX chromosomes. One Barr body means the female has two X chromosomes. Turner's syndrome (44 + XO) is a genetic disorder that affects only females. In this condition, cells of the affected female possess only one X chromosome, instead of two. Due to the presence of only one X chromosome, no Barr body is present in females suffering from Turner's syndrome
Which is genetically not possible
Haemophilic father transfers the haemophilic gene to his son.
Haemophilic father transfers the haemophilic gene to his daughter.
Carrier mother transfers the haemophilic gene to her son.
Carrier mother transfers the haemophilic gene to her daughter
A.
Haemophilic father transfers the haemophilic gene to his son.
Haemophilia is a sex linked disease. It follows criss-cross inheritance in which father does not pass the sex-linked allele of a trait to his son. The same is passed to the daughter, from where it reaches the grandson, i.e., diagynic. It is because the males have only one X-chromosome which is transferred to the female offspring. Only Y-chromosome of the father is transferred to the male offspring but this sex chromosome does not carry the allele for haemophilia. Mother passes the alleles of a sex-linked trait to both sons and daughters.
If 'A' represents the dominant gene and 'a' represents its recessive allele, which of the following would be the most likely result in the first generation offspring when Aa is crossed with aa ?
All will exhibit dominant phenotype
All will exhibit recessive phenotype
Dominant and recessive phenotypes will be 50% each
Dominant phenotype will be 75%
C.
Dominant and recessive phenotypes will be 50% each
'A' represents the dominant gene and 'a' represents its recessive allele. The most likely result in the first generation offspring when Aa is crossed with aa is :
Parents : Aa aa
Gametes : A, a, a, a
F1 generation : Aa Aa aa aa
Hence, Aa : aa = 1 : 1
Assertion : Foetal disorders can be diagnosed by chorionic villi sampling.
Reason : Karyotyping can be done for mitotically dividing cells of chorionic villi.
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
A.
If both assertion and reason are true and reason is the correct explanation of assertion.
During early pregnancy, foetal disorders can be diagnosed using chorionic villi sampling. In this technique the physician inserts a narrow, flexible tube through the mother's vagina and cervix into the uterus (guided by ultrasound) and withdraws a small amount of foetal tissue (chorionic villi) from the placenta. Because the cells ofthe chorionic villi are undergoing rapid mitosis, these cells can be used for karyotyping.
Assertion : Curdling is required in the manufacture of cheese.
Reason : Lactic acid bacteria are used for the purpose.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
C.
If assertion is true but reason is false
Chromosomal or allosomic determination of sex is based on heterogamety or occurence of two types of gametes in one of the two sexes. Male heterogamety is found in allosome complements XX-XY and XX-XO. In birds and some reptiles both the sexes possess two sex chromosomes but unlike human beings the females contain heteromorphic sex chromosomes (AA + ZW) while the males have homomorphic sex chromosomes (AA + ZZ).
Assertion : Number of chromosomes in one genome is equal to number of linkage groups.
Reason : Linkage groups give important information about the location of genes in the chromosomes.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false
If both assertion and reason are false
B.
If both assertion and reason are true but reason is not the correct explanation of assertion.
Linkage group, in genetics, all of the genes on a single chromosome. They are inherited as a group; that is, during cell division they act and move as a unit rather independently. The existance of linkage groups is the reason some traits do not comply with Mendel's law of independent assortment; ie, the principle applies only if genes are located on different chromosomes.
Which of the following occurs due to monosomy of sex chromosome
Down's syndrome
Turner's syndrome
Haemophilia
Sickle cell anaemia
B.
Turner's syndrome
Turner's syndrome is caused due to the absence of one of the X chromosomes i.e., 45 chromosomes total with sex chromosomes as XO. Such females are sterile as ovaries are rudimentary. Besides this, other features include lack of other secondary sexual characters, etc.
Assertion: In a pedigree analysis, <5> represents five unaffected offsprings.
Reason: In a pedigree analysis, the offsprings are numbered with arabic numerals (1, 2, 3 .....) and a generation is numbered with roman numerals (I, II, III...).
If both assertion and reason are true and reason is the correct explanation of assertion.
If both assertion and reason are true but reason is not the correct explanation of assertion.
If assertion is true but reason is false.
If both assertion and reason are false.
B.
If both assertion and reason are true but reason is not the correct explanation of assertion.
Percentage of recombination between A and B is 9%, A and C is 17%, B and C is 26% , then the arrangement of genes is
ABC
ACB
BCA
BAC
D.
BAC
One map unit or centimorgan is equivalent to 1% recombination between two genes. The frequency of recombination can be used to depict the arrangement of the genes.
Recombination frequency between three genes is:
(i) A - B = 9%
(ii) A - C = 17%
(iii) B - C = 26%
By manipulating all the three possibilities of their arrangements A - B -C, A -C - B and B - A - C, it was found that the three gene must be arranged in the order B - A - C with distance B - A = 9 cM and A - C = 17 cM and the distance being 26 cM.
Which of the following conditions represents a case of co-dominant genes?
A gene expresses itself, suppressing the phenotypic effect of its alleles
Genes that are similar in phenotypic effect when present separately, but when together interact to produce a different trait
Alleles, both of which interact to produce a trait, which may or may not resemble either of the parental types
Alleles, each of which produces an independent effect in a heterozygous condition
D.
Alleles, each of which produces an independent effect in a heterozygous condition
Co-dominance is the phenomenon when the two genes neither show dominant-recessive relationship nor show intermediate condition, but both of them express themselves simultaneously. Eg, Patches of two different colours on the skin.
Assertion : A gamete may carry either of the traits but not both.
Reason : This is Mendel's second law or law of independent assortment.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
C.
If assertion is true but reason is false
The law of segregation states that the two alleles controlling each character maintain identity in the organism but during the formation of gametes or spores by meiosis move apart due to separation of the homologous chromosomes which bear them, so that each gamete or spore receives only one allele of each character on random basis.
Since the gametes or spores possess one allele of each character, they are always pure. The law of segregation is, therefore, also called the law of purity of gametes/spores.
Mendel's second law or the law of independent assortment states that the alleles of different characters located in different pairs of homologous chromosomes are independent of one another in their segregation during gamete formation and in coming together into the offspring by fertilization, both processes occurring randomly.
The distance between two genes in a chromosome is measured in cross-over units which represent
ratio of crossing over between them
percentage of crossing over between them
number of crossing over between them
none of these.
B.
percentage of crossing over between them
The physical distance between two genes determines both the strength of the linkage and the frequency of the crossing over between two genes. The strength of the linkage increases with the closeness of the two genes. On the other hand the frequency of crossing over increases with the increase in the physical distance between the two genes
Assertion: Persons suffering from haemophilia fail to produce blood clotting factor VIII.
Reason: Prothrombin producing platelets in such persons are found in very low concentration.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false.
C.
If assertion is true but reason is false
Haemophilia, also called bleeder's disease is a X-linked recessive disorder. The person which contains the recessive gene for haemophilia lacks a normal clotting substance (thromboplastin) in blood. So minor injuries cause continuous bleeding and ultimate death of the person due to hemorrhages.
Haemophilia is of two types : type A characterized by lack of antihaemophilic globulin (factor VIII) and type B characterized by a defect in plasma thromboplastic component (factor IX).
Prothrombin is an inactive plasma protein and is produced by liver. It helps in blood clotting. It is not produced by platelets.
XO-chromosomal abnormality in human beings causes
Turner's syndrome
Down's syndrome
Klinefelter's syndrome
None of these
A.
Turner's syndrome
Turner's syndrome is characterised by the monosomy of XO type. It is characterized by a lack of ovaries and menstrual cycle. Affected women are sterile and lack secondary sexual characteristics, although the external genitalia are present. The syndrome is named after the US endocrinologist H. H. Turner (1892- 1970).
Down's syndrome is a congential form of mental retardation due to a chromosome defect in which there are three copies of chromosome no. 21 instead of the usual two (XXX). The affected individual has a short broad face and slanted eyes (as in the Mongolian races), short fingers, and weak muscles. It can be detected before birth by amniocentesis. It is named after the British physician John Down ( 1828- 96).
Klinefelter's syndrome is characterised by trisomy (XXY). These are male individuals, who are phenotypically fairly normal but have a fairly low sperm count and are therefore sterile.
If a homozygous red-flowered plant is crossed with a homozygous white-flowered plant, the offsprings will be
half- white flowered
half- red flowered
all white flowered
all red flowered
D.
all red flowered
The red colour of flower dominates upon white colour of flower. In the present varieties both parents are of pure variety, therefore, the offsprings will be all heterozygous red flowered as shown below:
Parents RR rr
(Red flowered) (White flowered)
Gametes R R r r
F1 generation Rr Rr Rr Rr
(offspring) (Heterozygous red flowered plants)
Gene which suppresses other gene's activity but does not lie on the same locus is called as
epistatic
supplementary
hypostatic
codominant
A.
epistatic
The phenomenon by which a gene suppresses the phenotypic expression of a non- allelic gene is called epistasis. In F2 generation, the ratio for epistatic gene is 12 : 3.
The alleles which do not show dominant recessive relationship and are able to express themselves independently when present together are called co- dominant alleles.
Supplementary genes are a pair of non- allelic genes, one of which produces its effect independently in the dominant state while the dominant allele of the second gene is without any independent effect. Although, it is able to modify the effect of the former to produce a new trait.
Pure line breed refers to
heterozygosity only
heterozygosity and linkage
homozygosity only
homozygosity and self assortment
C.
homozygosity only
Pure breeds are cultivated varieties or cultivars of an animal species, achieved through the process of selective breeding. Also, it is a true breeding genotypes, a line that has been rendered homozygous for all genes under consideration in successive generations, a line in which homozygous individuals produce only homozygous offspring like parents.
Assertion : Haemophilia is a recessive sex linked disease.
Reason : Haemophilia occurs due to mutation of a structural gene on chromosome 15.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false
C.
If assertion is true but reason is false
Haemophilia is also known as bleeder disease. It is an example of sex linked inheritance in humans. It is either of two hereditary disorders in which the blood clots very slowly, due to a deficiency of either of two coagulation factors -
The patient may experience prolonged bleeding following any injury or wound, and in severe cases there is spontaneous bleeding into muscles and joints. It is controlled by a sex-linked gene, which means that it is almost exclusively restricted to males; women can carry the disease- and pass it on to their sons- without being affected themselves. The genes encoding factors VIII and IX have been used in gene therapy trials for haemophilia.
Mutations of a structural gene on chromosome 15 is the molecular basis of Marfan syndrome. It is due to dominant mutation resulting in the production of abnormal form of connective tissues and characteritic extreme looseness of joints.
Which one of the following pairs of features is a good example of polygenic inheritance
Human height and skin colour
ABO blood group in humans and flower colour of Mirabilis jalapa
Hair pigment of mouse and tongue rolling in humans
Human eye colour and sickle cell anaemia
A.
Human height and skin colour
Polygenic inheritance is the inheritance pattern of a trail controlled by two or more genes. Genes may be on the same or different chromosomes and each gene may have two or more alleles. The gene expression is influenced by a variety of factors including gender, nutrition, breed, rate of growth, and amount of exercise. These traits are quantitative traits - that is, there is a wide range within the population. Such traits include height, weight, character, working abilities, and some genetic defects.
Mating of an organism to a double recessive in order to determine whether it is homozygous or heterozygous for a character under consideration is called
reciprocal cross
dihybrid crossn
test cross
back cross
C.
test cross
Test cross is a cross made to identify hidden recessive alleles in an individual of unknown genotype. This individual is crossed with one that is homozygous for the allele being investigated (i.e., a homozygous recessive). The homozygous recessive individual may be the parent of the individual being investigated.
In which one of the following sets of three items each belong to the category mentioned against them
Lysine, glycine, thiamine - amino acids
Myosin, oxytocin and gastrin - hormones
Rennin, helicase and hyaluronidase - enzymes
Optic nerve, oculomotor, vagus - sensory nerves
C.
Rennin, helicase and hyaluronidase - enzymes
Rennin, helicase and hyaluronicasc are all enzymes.
Rennin (chymosin), secreted by the stomach is responsible for clotting milk. It acts on a soluble milk protein (caseinogen) to converts it into the insoluble form casein.
Helicase unwinds double stranded helical DNA during replication.
Hyaluronidase is able to digest hyaluronic acid (major glycosaminoglycan) and is therefore important in modulating the removal of cell matrix in order to facilitate cell movement or tissue organization.
Thiamine is not an amino acid, it is vitamin B1, which is active in the form of thiamin pyrophosphate, a coenzyme in decarboxylation reactions in carbohydrate metabolism. A deficiency of vitamin B1 leads to beriberi.
Myosin is a contractile protein found in eukaryotic tissue. interacts with actin to bring about contraction of muscle or cell movement. Among optic, oculomotor and vagus, which are cranial nerves, optic is sensory in nature, oculomotor is motor and vagus is mixed sensory nerves.
Given below is a highly simplified representation of the human sex chromosomes from a karyotype
The gene a and b could be of colour blindness and body height
attached ear lobe and Rhesus blood group
haemophilia and red-green colour blindness
phenylketonuria and haemophilia
C.
haemophilia and red-green colour blindness
The figure shows, human sex chromosome with genes 'a'and b. So, 'a' and b' are sexlinked genes, that arc inherited through sex chromosomes. The most important character of sex linked inheritance are colourblindness and haemophilia. Both the disorders are due to recessive sex linked genes. The gene for red green colour blindness is located on X chromosomes. The person suffering from this disease is unable to distinguish red and green colours. Haemophilia, also called bleeder's disease, is due to presence of recessive gene on X-chromosome. The person suffering from this disease have blood which does not clot properly i.e, lacking a factor (plasma thromboplastin) which is responsible for clotting of blood.
Genes present in the cytoplasm of eukaryotic cells are found in
mitochondria and inherited via egg cytoplasm
lysosomes and peroxisomes
Golgi bodies and smooth endoplasmic reticulum
plastids and inherited via male gamete
A.
mitochondria and inherited via egg cytoplasm
Genes present in the cytoplasm of eukaryotic cells are found in the mitochondria and inherited via egg cytoplasm. Maternal inheritances are the genetic effects that are transmitted via the maternal line. There are many such effects some resulting from the purely maternal origin of mitochondria or chloroplasts. others from effects on the phenotype of the embryo by easily development within the female, such as maternal influence on coiling of snails.
Given below is a pedigree chart showing the inheritance ofa certain sex-linked trait in humans
The trait traced in the above pedigree chart is
dominant X- linked
recessive X- linked
dominant Y- linked
recessive Y- linked
A.
dominant X- linked
In the given chart, the disease is inherited by female child from his father and none of the male child is affected hence it shows that the disease is X linked. Also in the progeny the disease is expressed phenotypically by female child even if it is carrier, so the disease is dominant. Hence the pattern of disease is X linked dominant.
The 'cri-du-chat' syndrome is caused by change in chromosome structure involving
deletion
duplication
inversion
translocation
A.
deletion
Cri du chat is a rare syndrome caused by a deletion on the short arm of chromosome 5. It is a rare genetic disorder due to a missing portion of chromosome 5. It refers to a distinctive cry of children. The cry is mainly caused by abnormal larynx development, which becomes normal within a few weeks of birth. Infants with cri du chat have low birth weight and may have respiratory problems.
Grain colour in wheat is determined by three pairs of polygenes. Following the cross AABBCC (dark colour) x aabbcc (light colour), in F2 generation what proportion of the progeny is likely to resemble either parent?
None
Less than 5 percent
One third
Half
B.
Less than 5 percent
Polygene results in quantitative inheritance. Quantitative inheritance is characterised by occurrence of intermediate forms between the parental type. There will be 7 (1 : 6 : 15 : 20 : 15 : 6 : 1) phenotypes when three polygene pairs are involved. The total number of progeny would be 64. Out of these sixty four only two will be likely to resemble either parents. Hence their proportion in F2 generation would be 3.12 i.e. less than 5%.
Primary source of allelic variation is
independent assortment
recombination
mutation
polyploidy
B.
recombination
Recombination is the natural process of breaking and rejoining DNA strands to produce new combination of genes and, thus, generate genetic variation. This is the phenomenon which occur during meiosis I.
Independent Assortment is one of the law of Mendel. It states thats when two or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits an equal opportunity of occurring together.
Mutation is the alteration in the genetic material by physical or chemical changes.
Polyploidy is a state of a cell or organism having more than two homologous paired sets of chromosomes.
Assertion: Polytene chromosomes have a high amount of DNA.
Reason: Polytene chromosomes are formed by repeated replication of chromosomal DNA without separation of chromatids.
If both assertion and reason are true and reason is the correct explanation of assertion
If both assertion and reason are true but reason is not the correct explanation of assertion
If assertion is true but reason is false
If both assertion and reason are false.
A.
If both assertion and reason are true and reason is the correct explanation of assertion
Polytene chromosomes are quite common in salivary glands of insects and so are called salivary chromosomes. These chromosomes have high amount of DNA of almost I 000 times in Drosophila as compared to ordinary somatic chromosomes. These chromosomes are multistranded. They are in permanent prophase stage. These chromosomes& are formed by somatic pairing between homologous chromosomes and repeated replication pf their chromonemata without separation of chromatids. All the chromosomes may remain attached to one another at a common point called chromocentre.
A baby has been born with a small tail. It is a case exhibiting
retrogressive evolution
mutation
atavism
metamorphosis
C.
atavism
In biology, an atavism is a modification of a biological structure whereby an ancestral trait reappears after having been lost through evolutionary change in previous generations. Atavisms can occur in several ways, one of which is when genes for previously existing phenotypic features are preserved in DNA, and these become expressed through a mutation that either knocks out the overriding genes for the new traits or makes the old traits override the new one.
Given below is a representation of a kind of chromosomal mutation. What is the kind of mutation represented
Deletion
Duplication
Inversion
Reciprocal translocation
C.
Inversion
During inversion a segment of chromosome gets inverted in the process of reattachment. Thus a chromosome having the genes A B C D E F G H I in linear order may get the segment DEF inverted. The new arrangement will be A B C F E D G H I. It is a chromosome aberration entailing two breaks in a chromosome followed by a reversal of the segment and consequently ofthe gene sequence in the segment. Pericentric inversion includes the centromere in the inverted segment, whereas paracentric inversions do not.
How many different types of gametes can be formed by F1 progeny, resulting from the following cross
AA BB CC x aa bb cc
3
8
27
64
B.
8
Parent generation - AA BB CC x aa bb cc
F1 Generation - AaBbCc
Number of heterozygote is 3
Number of progenies in F1 will be 2n or 23= 8,
Assertion : In humans, the gamete contributed by the male determines whether the child produced will be male or female.
Reason : Sex in humans is a polygenic trait depending upon a cumulative effect of some genes on X chromosome and some on Y-chromosome.
If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion
If both Assertion and Reason are true but the Reason is not the correct explanation of the assertion
If Assertion is true but Reason is false
If both Assertion and Reason are false
C.
If Assertion is true but Reason is false
In humans, sex is determined by sex chromosomes. females consists of XX pair of sex chromosome and males consists of XY pair of sex chromosomes. Therefore, males determine the sex of the offspring. Sex in humans is monogenic trait.
Human skin, hair and eye colour are polygenic traits as they are influenced by more than one allele at different loci. the result is the perception of continuous gradation in the expression of these traits.
One of the genes present exclusively on the X-chromosome in humans is concerned with
baldness
red-green colour blindness
facial hair/moustaches in males
night blindness
B.
red-green colour blindness
The most common form of red-green colour blindness is an 'X chromosome linked recessive' disorder. The 'red' and 'green' genes are known to reside at the tip of the long arm of the X chromosome. Women have two copies of the X-chromosome, and so they may have normal colour vision, even if they carry one copy of the defective gene. Men have only one X-chromosome, and so will be colour blind.
Mirabilis jalapa is an example of
complete dominance
supplementary gene
incomplete dominance
complementary gene
C.
incomplete dominance
Incomplete dominance is the phenomenon of neither of the two alleles being dominant so that expression in the hybrid is intermediate between the expressions of the two alleles in homozygous state. Eg. Inheritance pattern in Mirabilis jalapa flower. In this plant, two allelomorphic pair of the genes are not related as dominant and recessive. But the dominant gene in heterozygous condition has reduced expression, so that each
of them expresses itself partially.
There are 2 types flower colour in pure state: red and white. When the two types of plants are crossed, hybrid or plants of F2 generation have pink flowers. If the latter are selfed, the plants of F2 generation are of 3 types- red, pink and white.
Which of the following is dominant character according to Mendel ?
Dwarf plant and yellow fruit
Terminal fruit and wrinkled seed
White testa and yellow pericarp
Green coloured fruit and rounded seed
D.
Green coloured fruit and rounded seed
Mendel studied seven pairs of contrasting characters.
| Characters | Dominant trait | Recessive trait |
| Stem height | Tall | Dwarf |
| Flower colour | Violet | White |
| Flower position | Axial | Terminal |
| Pod shape | Inflated | Constricted |
| Pod colour | Green | Yellow |
| Seed shape | Round | Wrinkled |
| Seed colour | Yellow | Green. |
Lack of independent assortment of genes A and B in fruit fly Drosophila is due to :
repulsion
linkage
crossing-over
recombination
B.
linkage
Mendel's law of independent assortment always fails where linkage is found i.e., lack of independent assortment of genes A and B in fruit fly Drosophila melanogaster is due to linkage.
This is mainly because when two traits were found not to assort completely independently. Linked genes do not independently assort. They are located on the same chromosome and that tend to be inherited together.
When two mutations are located in the same functional unit or in different functional units, then it is confirmed by :
test cross
back cross
reciprocal cross
complementation test
D.
complementation test
The functional allelism of any two recessive mutations is determined experimentally by cis-trans or complementation test. Complementry genes are two or more dominant genes which occur in different loci of the same or different chromosomes interact with one another to produce a character but neither of them produces that character in the absence of the other.
9: 3: 3: 1 ratio is modified to 9 : 7 ratio due to
complementary gene
epistatic gene
hypostatic gene
supplementary gene
A.
complementary gene
Complementary genes are the genes which are present on different genetic loci but interact with each other to express a single character in combination. That is they both together produce a particular phenotypic trait in an individual. Supplementary genes are the genes which include two pairs of non-allelic genes.
The map distance between the genes A and B is 3 units, between B and C is 10 units and between C and A is 7 units. The order of the genes in a linkage map constructed on the above data would perhaps be
A, B, C
A, C, B
B, C, A
B, A, C
D.
B, A, C
From the recombination frequencies between different genes A, B and C, it is clear that distance between A and B genes is 3 units between B and C is 10 units and C and A is 7 units. Hence, linear order of genes on chromosomes is
One of the following is sex-influenced character
Appearance of beard
Baldness in male
Docile behaviour of female
Low BMR in female
B.
Baldness in male
D.
Low BMR in female
Inheritance of pattern baldness in man is an example of sex-influenced trait which is dominant in males and recessive in females.
A person with the sex chromosomes XXY suffers from :
Down's syndrome
Turner's syndrome
Gynandromorphism
Klinefelter's syndrome
D.
Klinefelter's syndrome
Klinefelter's syndrome is a chromosomal abnormality due to which an individual has two X-chromosomes and one Y-chromosome ie, XXY. Such persons are sterile male and may exhibit secondary female characters.
Down syndrome is also known as Trisomy- 21. It is a genetic disorder caused by the presence of extra copy of chromosome on 21st chromosome.
Turner's syndrome is a chromosomal condition that affects development in females. It consists of only 45 pairs of chromosomes ie, it is represented as X0. Females with this type of disease have short stature.
A gynandromorph can have bilateral asymmetry; one side female and one side male. Alternatively, the distribution of male and female tissue can be more haphazard. Bilateral gynandromorphy arises very early in development, typically when the organism has between 8 and 64 cells.
Which of the following represents Klinefelter's syndrome?
XX
XO
XY
XXY
D.
XXY
Klinefelter's syndrome is a chromosomal abnormality due to which an individual has two X-chromosomes and one Y-chromosome ie, XXY. Such persons are sterile male and may exhibit secondary female characters. They also have underdeveloped genitalia, sparse body hair and exhibit some degree of breast development. They possess 47 chromosomes instead of normal 46 chromosomes. The interphase nuclei of their cells possess one barr body.
Which one of the following conditions in chromosome number is called monosomy?
2n + 1
2n + 2
2n - 1
2n - 2
C.
2n - 1
Monosomy is the condition of having a diploid chromosome complement in which one chromosome lacks its homologous partner. Eg, Turner's Syndrome.
In Turner's Syndrome, there is presence of 45 pair of chromosomes,ie, (2n - 1) XO. It occurs only in females. These females do not mature sexually and are sterile. They have Short stature and normal intelligence.
Tetrasomy or 2n + 2 is a form of aneuploid with the presence of four copies of chromosomes.
Trisomy or 2n + 1 is a chromosomal disorder characterised by an additional chromosome. Eg, Down's syndrome, Patau's syndrome etc.
Nullisomy or 2n-2 is a genetic condition involving the lack of both the normal chromosomal pair for a species.
Down's syndrome occurs as a result of
trisomy
tetrasomy
autopolyploidy
allopolyploidy
A.
trisomy
Down's Syndrome is Trisomy of 21st chromosome. It is characterized by mental retardation, short stature with stubby fingers and heart defects.
Indicate, the inheritance of which of the following is controlled by multiple alleles?
Colourblindness
Sickle cell anaemia
Blood group
Phenylketoneuria
C.
Blood group
A particular gene has been found to occur in two alternative forms or allelomorphs. The existence of more than two allelic forms of a gene is called multiple allelism and the alleles as multiple alleles, eg, blood group in human.
Which of the following conditions is related to haemophilia?
A responsible recessive gene present in the X-chromosome
A responsible dominant gene presentin the X-chromosome
A responsible dominant gene present in the Y-chromosome
A responsible dominant gene present in the autosomal chromosome
A.
A responsible recessive gene present in the X-chromosome
Haemophilia is the most serious and notorious disease which is more common in man than in woman. The person which contains the recessive gene for haemophilia lacks normal clotting substance (thromboplastin) in blood so, amino injuries cause continuous bleeding and ultimate death. It is X-linked disease.
The absence of which clotting factor leads to haemophilia-A?
Factor VII
Factor VIII
Factor IX
Factor X
B.
Factor VIII
Haemophilia-A is characterized by lack of antihaemophilic globulin (factor VIII). Haemophilia is caused due to X-linked recessive gene.
A character, which is expressed in a hybrid is called
dominant
co-dominant
recessive
epistaticn
A.
dominant
Dominance in genetics is a relationship between alleles of one gene, in which the effect on phenotype of one allele masks the contribution of a second allele at the same locus.
Which of the following is correct
Haemophilic-Y-chromosome
Down's syndrome-21' chromosome
Sickle cell anaemiaX-chromosome
Parkinson's disease-X and Y-chromosome
B.
Down's syndrome-21' chromosome
Down syndrome (DS or DNS), also known as trisomy 21, is a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is typically associated with physical growth delays, mild to moderate intellectual disability, and characteristic facial features.
Test cross is a cross between
hybrid and dominant parent
hybrid and recessive parent
two hybrid parents
two distantly related species
B.
hybrid and recessive parent
Test cross is a simple method devised by Mendel to verify the genotype of the F1 hybrid. When the F1 hybrid is crossed with the homozygous recessive parent, it is called a test cross.
Which of the following condition is called monosomic?
2n + 1
2n + 2
n + 1
2n - 1
D.
2n - 1
A cell or individual that is basically diploid but that has only one copy of one particular chromosome type and thus, has chromosome number 2n - 1 is known as monosomic condition.
What is a test cross? Why is it so named?
The cross of F1 hybrid with that of its homozygous recessive parent is called test cross. It is so named because it determines whether the F1 individual is homozygous or heterozygous dominant.
Polyploid derived from two different species is called
autopolyploid
triploid
allopolyploid
monoploid
C.
allopolyploid
A polyploid having two or more distinct genome usually produced by chromosome doubling of interspecific hybrids is called allopolyploid or interspecific polyploid.
Autopolyploidy is any individual or strain whose chromosome complement consists of more than two complete copies of the genome of a single ancestral species.
Triploid is a rare chromosomal abnormality. It causes an extra set of chromosomes in their cells.
Monoploid is a cell or an organism that has a single set of chromosomes.
The gene of sickle cell anaemia is inherited by
blood cells
bone cells
sex chromosomes
autosomes
D.
autosomes
Sickle cell anaemia is a genetic disorder reported from negroes due to a molecular mutation of gene Hb on chromosome 11 (autosome) which produces the B-chain of haemoglobin. In sickle-cell anaemia the sixth amino acid of haemoglobin (ie, glutamic acid) is replaced by valine.
How many pairs of contrasting characters in pea pod were chosen by Mendel?
3
5
7
9
A.
3
The number of characters studied by Mendel was seven which are present on four chromosomes.
| Characters | Dominant | Recessive |
| Stem height | Tall | Dwarf |
| Flower colour | Violet | White |
| Pod position | Axial | Terminal |
| Pod shape | Inflated | Constricted |
| Pod colour | Green | Yellow |
| Seed shape | Round | Wrinkled |
| Seed colour | Yellow | Green |
Three contrasting characters with respect to pea pod are (i) pod shape, (ii) pod colour, (iii) pod position.
If a cross between two individuals produces offsprings with 50% dominant character (A) and 50% recessive character (a) the genotype of parents are
Aa Aa
Aa aa
AA aa
AA Aa
B.
Aa aa
A cross between homozygous recessive and heterozygous plant is called test cross. It gives 1 : 1 ratio in monohybrid and 1 : 1 : 1 : 1 radio in dihybrid cross.
Which pairs of the following diseases are caused by two genes located on human X-chromosomes?
Colour blindness and phenylketonuria
Colour blindness and haemophilia
Colour blindness and albinism
Colour blindness and hypertrichosis
B.
Colour blindness and haemophilia
X- linked recessive inheritance is a mode of inheritance in which a mutation in a gene on the X- chromosome causes the phenotype to be expressed in males. Colour blindness and haemophilia both are the examples of X-linked recessive traits.
Which one of. the following animals possesses giant chromosome?
Drosophila
Mouse
Pigeon
Elephant
A.
Drosophila
Polytene chromosomes or salivary chromosomes are the giant chromosomes discovered by Balbiani (1881) in the salivary glands of Chironomous tantans. Later they were found in the salivary glands and Malpighian tubules) of many insect larvae including Drosophila.
A man having the genotype EEFfGgHH can produce P number of genetically different sperms and a woman of genotype IiLLMmNn can generate Q number of genetically different eggs. Determine the values of P and Q.
P - 4; Q - 4
P - 4; Q - 8
P - 8; Q - 4
P - 8; Q - 8
B.
P - 4; Q - 8
The given genotype of man = EEFfGgHH
P = 2n = 22 = 4 (where, n = number of heterozygotes)
i.e., EFGH, EfGH, EFgH, EfgH.
The given genotype of woman = IiLL Mm Nn
Q = 2n = 23 = 8 (where, n = number of heterozygosity)
i.e., ILMN, ILmN, ILMn, ILmn, iLMN, iLmN, iLMn, iLmn.
In an organism, tall phenotype is dominant over recessive dwarf phenotype and the alleles are designated as T and t, respectively. Upon crossing two different individuals, total 250 offsprings were obtained, out of which 124 displayed tall phenotype and rest were dwarf Thus, the genotype of the parents were
TT TT
TT tt
Tt Tt
Tt tt
D.
Tt tt
The cross between recessive homozygous parent and F1 hybrid (heterozygous) individual is called test cross and it gives only one type of result, i.e. 1 : 1 in any case.
Which of the, following statements is not true of two genes that show 50% recombination frequency?
the genes may be on different chromosomes
the genes are tightly linked
the genes show independent assortment
if the genes are present on the same chromosome, they undergo more than one cross overs in every meiosis
B.
the genes are tightly linked
The tightly linked genes on chromosomes show 100% parental types and 0% recombinants. Two genes that undergo independent assortment indicated by a recombinant frequency of 50% are either on non- homologous chromosomes or located far apart in a single chromosome. As the distance between two genes increases, crossover frequency increases. More recombinant gametes, fewer parental gametes.
If two persons with 'AB' blood group marry and have sufficiently large number of children, these children could be classified as 'A' blood group : 'AB' blood group : 'B' blood group in 1 : 2 : 1 ratio. Modern technique of protein electrophoresis reveals presence of both 'A' and 'B' type proteins in 'AB' blood group individuals. This is an example of
codominance
incomplete dominance
partial dominance
complete dominance
A.
codominance
In codominance both alleles of a pair express themselves fully in F1 hybrid. It is contrary to the situation seen in incomplete dominance, where traits express themselves only partially. This is not the example of partial dominance or complete dominance
AB IAIB Antigen A + Antigen B Codominance
Which Mendelian idea is depicted by a cross in which the F1 generation resembles both the parents?
Incomplete dominance
Law of dominance
Inheritance of one gene
Codominance
D.
Codominance
In codominance, both alleles of a pair express themselves fully in F1 hybrid, so, it resembles both the parents.
In incomplete dominance, the two genes of allelomorphic pair are not related as dominant or recessive, but each of them express itself partially.
Law of dominance states that when a cross is made between two homozygous individuals considering contrasting trait of simple character then the trait appear in F1 hybrids is called dominant inheritance of one gene is based on crossing between single traits.
The incorrect statement with regard to haemophilia is
it is a sex-linked disease
it is a recessive disease
it is a dominant disease
a single protein involved in the clotting of blood is affected
C.
it is a dominant disease
Haemophilia is a sex linked recessive disease. A single protein that is a part of the cascade of protein is involved in the clotting of blood is affected. The heterozygous female for haemophilia may transmit the disease to sons.
If both parents are carriers for thalassemia, which is an autosomal recessive disorder, what are the chances of pregnancy resulting in an affected child?
No chance
50%
25%
100%
C.
25%
Thalassemia is the disorder due to reduced synthesis of either the or - chains, likewise designated as or - thalassemias. When this autosomal mutant gene is present in double dose, it is known as thalassemia major.
The frequency of crossing-over occurring between two genes located on the same chromosome depends on
length of the chromosome
position of the centromere
activities of two genes
distance between two genes
D.
distance between two genes
The frequency of crossing-over occurring between the two genes located on the same chromosome is only directly proportional to the distance between the two genes. Hence, the closer the two genes are to one another on a chromosome, the greater will be their chance of being inherited together.
However, genes located farther away from each other on same chromosome are more likely to be separated during recombination. Other factors giving in the options such as length of chromosome, position of centromere and activities of two genes does not have any relation with the crossing-over and recombination.
Anish is having colour blindness and married to Sheela, who is not colourblind. What is the chance that their son will have the disease?
100%
50%
25%
0%
D.
0%
Colour blindness is a sex-linked recessive disorder, which results in defects in either red or green cone of an eye which ultimately leads to the failure in discriminating between red and green colour. The gene for colour blindness is located on X-chromosome.
If a colourblind man marries a normal women the chances for their son to be colourblind is 0% because son will receive X-chromosome from his mother (who is not colourblind) and Y from the father (as gene of colour blindness is present on X, so Y chromosome is not affected at all). Thus, there is no chance for their son to be affected. Infact their girl child (daughter) will be the carrier of the disease.
In a plant species, flower colour yellow is dominant over white and fruit shape round is dominant over elongated. Crossing was performed between two pure lines - one having yellow-flower and round-fruit and another with white-flower and elongated-fruit. About 20 plants survived in F1 progeny. Plants of F1 were allowed to self-fertilise and about 960 plants survived in F2. If the traits follow Mendelian inheritance, the number of plants would have yellow-flower and round-fruit in F1 and F2 are respectively
20, 960
20, 540
10, 180
10, 60
B.
20, 540
Ratio of the species is as followes:-
Yellow Rounded : Yellow Elongated : White Rounded : White Elongated
4 : 3 : 3 : 1
Now, out of total 960 species survived in F2 generation. The number of plants that would have yellow flower and round fruit in F2 generation will be
(Total survived) = 540 plants.
Thus, in F1 and F2 -generation, total yellow colour, round fruit plants survived will be are 20, 540.
A set of genes will be in a complete linkage when the progeny phenotypes for parental (P) and recombinant (R) types are
P = 0%, R =100%
P = 50%, R = 50%
P < 50%, R > 50%
P = 100%, R = 0%
D.
P = 100%, R = 0%
A set of genes will be in a complete linkage when they are present in close proximity on a chromosome and are inherited together during meiosis always. Complete linkage means no crossing over or recombination, i.e. the progeny phenotypes will be totally parental. i.e., P=100%, R = 0%
Persons suffering from sickle-cell anaemia normally do not suffer from
cholera
malaria
high blood pressure
hepatitis
B.
malaria
Sickle-cell anaemia is a blood disease in which blood cells reveal an abnormal crescent (sickle) shape due to the point mutation at 6th position of -haemoglobin chain (glutamic acid valine). The resulted sickle-shape RBCs are resistant to attack by Plasmodium the vector of malarial disease.
Which one of the following information is essential to, determine the genetic map distance between two genes located on the same chromosome?
Length of the particular chromosome
Number of genes present in the particular chromosome
Number of nucleotides in the particular chromosome
Percentage of crossing over or recombinant frequency between the two genes
D.
Percentage of crossing over or recombinant frequency between the two genes
The frequency of recombination or percentage of crossing over between gene pairs on the same chromosome was used as a measure of the distance between genes and mapped their position on the chromosome.
This technique is based on the assumption that the farther apart two genes are on a chromosome, the higher the probability that a cross over will occur between them.
Which one of the following statements is relevant to sex linked characters?
They always follow criss-cross inheritance
They do not follow criss-cross inheritance
They are mostly present on Y-chromosome
They are only present on X-chromosome
A.
They always follow criss-cross inheritance
Sex-linked characters are the X-linked characters. Their inheritance is due to the X-linked genes. The X-linked recessive characters follow criss-cross pattern of inheritance or skip-generation inheritance. In criss-cross inheritance, character is inherited to the second generation through the carrier of first generation.
A male rabbit of genotype 'AABBDDEE' is crossed with a female rabbit of genotype 'aabbddee' to produce F1 hybrid offspring. How many genetically different gametes can be produced by this F1 hybrid?
4
8
16
32
C.
16
Types of gametes formed = 2n
24 = 2 x 2 x 2 x 2 = 16 gametes.
Match the items in column I with those in column II and choose the correct answer.
| Column I | Column II |
| A. Klinefelter syndrome | 1. Mutation in autosomal gene |
| B. Thalassaemia | 2. Mutation in sex chromosome linked gene |
| C. Down syndrome | 3. Trisomy of autosome |
| D. Colour blindness | 4. Trisomy of sex chromosme |
A- 1; B- 2; C- 3; D- 4
A- 2; B- 3; C- 4; D- 1
A- 3; B- 4; C- 1; D- 2
A- 4; B- 1; C- 3; D- 2
D.
A- 4; B- 1; C- 3; D- 2
| Column I | Column II |
| A. Klinefelter's syndrome | 4. Trisomy of sex chromosme (44 + XXY) |
| B. Thalassaemia | 1. Mutation in autosomal gene |
| C. Down's syndrome | 3. Trisomy of autosome (extra 21 chromosme) |
| D. Colour blindness | 2. Mutation in sex chromosome linked gene |
Choose the correct statements regarding genetic disorders.
I. Turner's female is result of aneuploidy.
II. Tritanopia is a sex-linked recessive disorder.
III. Haemophilia-C follows criss-cross pattern of inheritance.
IV. Sickel cell anaemia is due to mutation of alleles in chromosome 11.
I, IV
II, III
I, III
II, III
A.
I, IV
Statement I and IV are correct. Other statements can be corrected as:
III) Haemophilia -C is a mild form of haemophilia affecting both sexes.
(II) Tritanopia is a colour blindness for blue-yellow colour. It is a rare colour vision disturbance. It is caused by heterozygous mutation.
The type of mutation in the nucleotide sequence given below is
Transition
Transversion
Deletion
Inversion
D.
Inversion
Inversion mutation causes distortion of DNA. The mutation or a mutagen can change the base sequence of a cistron in the reverse order. A new sequence is formed with different codons.
Marfan syndrome, a dominant single gene defect is characterised by lens dislocation, long limbs, spindly fingers, caved in chest and weakened aorta. This is an example of
Complete dominance
Epistasis
Pleiotropy
Codominance
C.
Pleiotropy
Pleiotropy is the ability of a gene to have multiple phenotypic effects as it influence multiple characters simultaneously. It is not essential that all the traits are equally influenced.
Study the following statements.
I. F1 -progeny is the first hybrid generation and progeny resembles either of the two
parents.
II. F2 progeny is a resultant hybrid generation of cross pollination among F1 progeny and progeny shows retain as such both drawf and tall plants.
III. F2 progeny is second hybrid generation, produced by selfing F1 hybrids and progeny contained both drawf and tall plants.
IV. The proportion of probability of plants that were drawf were 1/4th of the F2 plants while 3/4th of the F2 plants were tall.
The correct statements are
I, II, III, IV
I, III, IV
I, II, IV
III, IV
B.
I, III, IV
Statement III can be corrected as follows-
In F2 generation self-pollination is done, not the cross pollination between F1 hybrids.
In sweet pea, C and P genes are essential for flower colour. In absence of either or both the genes, the flowers are white. What will be the percentage of coloured flowers in the offspring of cross Ccpp x ccPp?
75%
25%
80%
50%
B.
25%
The mentioned cross in the question is a dihybrid.
Ccpp x ccPp (both are white)
Hence, ratio of coloured to white flowers is 1:3.
Therefore, the percentage of coloured flowers in offsprings is 25%.
A women with albinic father marries an albinic man. The proportion of her progeny is
2 normal : 1 albinic
All normal
All albinic
1 normal : 1 albinic
D.
1 normal : 1 albinic
Albinism is an autosomal recessive metabolic disorder. It is characterised by the complete or partial absence of pigment in the skin, hair and eyes due to the absence or defect of tyrosinase, a copper-containing enzyme involved in the production of melanin.
An albino man (rr) marries a normal women (RR). Their progeny carries one recessive allele (r) and one dominant allele (R), i.e. it is heterozygous. When this heterozygous daugther (Rr) marries albinic man (rr), the proportion of her progeny found out to be 1 albino and 1 normal.
Who formulated the chromosomal theory of linkage
T H Morgan and W Castle
Stern and Hotta
Pontecarvo
Bridges and Burns
A.
T H Morgan and W Castle
Morgan along with Castle formulated the chromosome theory of linkage. According to this theory the gene shows the phenomenon of linkage situated on the same chromosome and the closely related genes shows strong linkage while distant gene show weak linkage.
A pea with white flower was crossed with another pea with white flower. When they selfed, the F2 generation produced purple and white in the ratio of 9:7. The reason for the result is that
it is typical monohybrid Mendelian ratio
purple flower colour is dominant over white
it is a complementary factor
None of the above
C.
it is a complementary factor
Complementary genes are the exception of Mendelian inheritance, in which two gene combinely produce a phenotype, which is not coded or expressed by a gene or allele alone.
The gene controlling seven traits in pea studied by Mendel were later found to be located on the following number of chromosomes
seven
four
five
six
B.
four
Seven traits selected by Mendel in pea are now known to be located on only 4 chromosomes, i.e., on 1, 4, 5 and 7 chromosomes. The characters are known as contrasting characters as these have one dominant and one recessive forms.
The crossing of a homozygous tall pea plant and homozygous dwarf pea plant would yield plants in the ratio of
2 tall : 2 dwarf
all heterozygous tall
all homozygous dwarf
one homozygous tall; one homozygous dwarf; two heterozygous tall
B.
all heterozygous tall
Homozygous tall - TT
Homozygous dwarf - tt
Parent generation : TT x tt
Gamete : T x t
F1 generation : Tt
The offsprings obtained by mating two pure strains having constrasting characters are called as
mutants
hybrids
F2 - generation
P - generation
B.
hybrids
Hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction.
Mutants are organisms, which are produced due to mutations.
F2 is the second filial generation.
P is parental generation.
What is not true about alleles?
Round and wrinkled form of genes are alleles of each other
Only recessive alleles expreses in hybrid
Alleles occupy same loci on homologous chromosomes
Two or more alternative forms of gene are called alleles are allelomorphs
B.
Only recessive alleles expreses in hybrid
The two alternative form of a gene are called alleles, e.g., the allele for tallness is T and that of dwarfness is t and dominant allele is expressed in hybrid.
In Mendelian monohybrid cross, phenotypic ratio in F2 is 3 :1. How many types of gametes are formed in F1 -generation?
Two types
Four types
Eight types
Only one types
A.
Two types
Parents- RR x rr
Gametes- R x r
F1 generation- Rr
F2 generation-
| R | r | |
| R | RR | Rr |
| r | Rr | rr |
Red : White = 3 : 1
Mendel enunciated
two principles of inheritance
four principles of inheritance
five principles of inheritance
three principles of inheritance
C.
five principles of inheritance
Mendel enunciated three major principles of inheritance, i.e., law of dominance, law of segregation and law of independent assortment.
Rarely observed phenotype in population is called
wild type
mutant type
variant type
All of these
B.
mutant type
Wild type refers to a strain, organism or gene, that is predominant in the wild population, while mutant form is observed rarely.
If a boy's father has haemophilia and his mother has one gene for haemophilia, what is the chance that the boy will inherit the disease?
100%
50%
0%
75%
B.
50%
Haemophilia is a X-linked recessive disorder. The presence of single X-chromosome (with haemophilia gene) show the disease in male. Therefore, in the above example, boy chances of inheriting the disease is 50%.
Pureline breed refers to
homozygosity
heterozygosity
homozygosity with only dominant genes
heterozygosity and linkage
A.
homozygosity
Pure line breed refers to a group of identical individuals that always produce offspring of the same phenotype when intercrossed. This occurs only when they are homozygous.
Barr-body in mammals represents
one of the two X-chromosomes in the cells
all heterochromatin of male and female cells
Y-chromosome of male
all heterochromatin of female cells
A.
one of the two X-chromosomes in the cells
Barr-body in mammals represent one of the two X-chromosomes in cells of female. It represents the facultative heterochromatin of inactivated X-chromosome.
Discontinuous variations are
essential features
acquired character
non-essential changes
heritable changes
D.
heritable changes
Discontinuous variations are sudden changes in the population characters that leads to new characters. It is also known as mutation. These are heritable changes, that is, they are or can be transmitted from parents to offsprings.
The linkage map of X-chromosome of fruit-fly has 66 units, with yellow body gene (y) at one end and bobbed hair (b) gene at the other end. The recombination frequency between these two genes (y and b) should be
50%
100%
66%
> 50%
B.
100%
The actual distance between two genes is said to be equivalent to the percentage of crossing over between these rwo genes. Since the two genes lie at the ends of the chromosome, there are 100 per cent chance of their segregation during crossing over.
In Drosophila, the sex is determined by
the ratio of pairs of X-chromosomes to the pairs of autosomes
whether the egg is fertilised or develops parthenogenetically
the ratio of number of X- chromosomes to the set of autosomes
X and Y-chromosomes
C.
the ratio of number of X- chromosomes to the set of autosomes
In Drosophila, the sex is determined by ratio of the number of X-chromosomes to the sets of autosomes. According to balance theory of sex determination, Y-chromosome of Drosophila is not important for the determination of sex.
Down's syndrome is caused by an extra copy of chromosome number 21. What percentage of a normal father would be affected by this disorder?
50%
25%
100%
75%
A.
50%
Down's syndrome is the result of trisomy in which chromosome number 21st contains an extra copy of chromosome (2A + 1). Affected mother will produce 50% normal egg cells and rest 50% eggs are of abnormal type.
Genetic map is one that
shows the stages during the cell division
shows the distribution of various species in a region
establishes sites of the genes on a chromosome
establishes the various stages in gene evolution
C.
establishes sites of the genes on a chromosome
Genetic map is a diagram, which shows the relative position of genes on a chromosome.
Mirabilis jalapa shows
codominance
incomplete dominance
dominance
complementary genes
B.
incomplete dominance
Mircbilis jalapa shows incomplete dominance. Here, two genes of allelomorphic pair are not related asrecessive and dominant but in heterozygous condition, both genes express itself partially. This is incomplete dominance.
Which of the following is not related to sex chromosome X or Y?
Turner's syndrome
Klinefelter's syndrome
Down's syndrome
Haemophilia and colour bindness
C.
Down's syndrome
Down's syndrome is not related to sex chromosome X or Y. It is due to the trisomy of 21st chromosome. The main characteristics are mental deficiency, short stature, round face, flaccid muscles, small ears, protruding tongue and epithelial folds over the eyes.
A normal woman is married with a man having hypertrichosis condition. They got one daughter and one son. What is the possibility of this daughter to have hypertrichosis condition?
0%
25%
50%
100%
A.
0%
The inheritance of hypertrichosis is controlled by holandric genes present on the non-homologous part of Y-chromosome. These genes are usually received and usually expressed by all the male descendants of affected male generation after generation while female descendants, being lacking this non-homologous Y-region could neither receive, express, nor transmit such a trait.
A woman has a haemophilic son and three normal children. Her genotype and that of her husband with respect to this gene would be
XX and XhY
XhXh and XhY
XhXh and XY
XhX and XY
D.
XhX and XY
In the above figure,
XhX - Carrier daughter
XhY - Haemophilic son
XX - Normal daughter
XY - Normal son
Hence, the correct genotype is XhX and XY.
The trisomy for 21st chromosome is called
Down's syndrome
Turner's syndrome
Sickle cell anaemia
Klinefelter's syndrome
A.
Down's syndrome
Trisomy of 21st chromosome is known as Down's syndrome.
Turner's syndrome is the non- disjunction of sex chromosome, that is, 2n = 45.
Klinefelter's syndrome is the presence of one extra chromosome, that is, 2n = 47.
Sickle cell anaemia is a disease in which RBCs are sickle in shape. It is a molecular gene mutation of gene HbA.
Which of the following is a test cross ?
Tt x tt
TT x tt
Tt x Tt
tt x tt
A.
Tt x tt
A test cross is a cross between heterozygous F1 hybrid and recessive homozygous parent eg. Tt x tt to show whether F1 is homozygous or heterozygous.
1 : 2 : 1 phenotypic and genotypic ratio is found in
complementary genes
blending inheritance
multiple alleles
pseudo alleles
B.
blending inheritance
Incomplete dominance or blending inheritance was first seen in Mirabilis jalapa (4'O clock plant). Here when red flowers are crossed with white flowers variety the F1 hybrid is pink and F2 ratio is 1 red : 2 pink : 1 white.
Tay Sach's disease is due to
sex linked recessive gene
sex linked dominant gene
autosomal dominant gene
autosomal recessive gene
D.
autosomal recessive gene
Tay Sach's disease is a recessive autosomal disorder which appear after birth due to deficiency of enzyme ,D-N-acetyl hexosaminidase. It results damage of brain and spinal cord and death at the age of 3-4 years.
Autosomes in humans are
11 pairs
22 pairs
23 pairs
43 pairs
B.
22 pairs
In humans, there are 22 pair of autosomes and 1 pair of sex chromosomes. Autosomes are the chromosomes which are not associated with sex.
A colourblind mother and normal father would have
colourblind sons and normal/carrier daughters
colourblind sons and daughters
all colourblind
all normal
A.
colourblind sons and normal/carrier daughters
Colourblindness is a sex linked defect in which human beings are unable to distinguish red and green colour. The gene for colourblindness is located on X- chromosome.
Colourblind mother - XcXc
Normal father - XY
| Xc | Xc | |
| X | XcX | XcX |
| Y | XcY | XcY |
They would have colourblind sons, i.e. XcY and carrier daughters, i.e. XcX.
Inheritance of ABO blood groups illustrates
polyploidy
multiple allelism
euploidy
dominance
D.
dominance
Inheritance of ABO blood groups is an example of multiple allelism. Multiple alleles are three or more alternative forms of genes or alleles occupying the same locus. Bernstein (1925) proposed that inheritance of ABO blood types of man is determined by a series of three allelomorphic genes IA, IB and i.
Crossing over in diploid organisms is responsible for
dominance of genes
linkage between genes
recombination of linked genes
segregation of alleles
C.
recombination of linked genes
Crossing over is a process that produces new combinations (recombination) of genes by interchanging of corresponding segments between non-sister chromatids of homologous chromosomes ie, the crossing over is responsible for recombination of linked genes in diploid organisms.
First geneticist, father of genetics was
de Vries
Mendel
Darwin
Morgan
B.
Mendel
Gregor Mendel was the Father of Genetics. He was known as the Father because of his work on pea plants.
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