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Principles of Inheritance and Variation

Question
CBSEENBI12002208
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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

Solution

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.

Question
CBSEENBI12002179
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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

Solution

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.

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Question
CBSEENBI12002603
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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

Solution

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.

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Question
CBSEENBI12002265
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In his classic experiments on pea plants, Mendel did not use

  • Seed colour

  • Pod length

  • Seed shape

  • Flower position

Solution

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

Question
CBSEENBI11003723
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In Mendel's experiments with garden pea, round seed shape (RR) was dominant over wrinkled seeds (rr), yellow cotyledon (YY) was dominant over green cotyledon (yy). What are the expected phenotypes in the F2 generation of the cross RRYY x rryy?

  • Only round seeds with green cotyledons

  • Only wrinkled seeds with yellow cotyledons

  • Only wrinkled seeds with green cotyledons

  • Round seeds with yellow cotyledons and wrinkled seeds with yellow cotyledons

Solution

D.

Round seeds with yellow cotyledons and wrinkled seeds with yellow cotyledons

When a cross (dilhybrid) is made between plants bearing round yellow (RRYY) and wrinkled green (rryy) seeds, all the plants in F1 generation are with yellow round seeds (showing the genotype RrYy). The phenotype in F2 will be as follows:

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