(A) L.S. of an embryo of grass.
. 
B
i. Each anther of the angiosperm flower is bilobed in nature with two layered protection called theca (dithecous). Each theca is separated by longitudinal grooves. Bilobed nature is distinct in transverse section, microsporangia is located at the corners of the tetragonal structure. 

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. 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.

A. Characteristics features of cloning vector
1. Presence of Origin of replication (ori) - The vector should have an ori which is a sequence from where replication starts. Any piece of DNA which is linked to the ori can be made to replicate within the host cells. The ori site also controls the copy number so cloning vectors having ori that support a high copy number are chosen.
2. Selectable marker – The vector should possess a selectable marker which helps to distinguish and identify the non-transformants from transformants and selectively permit the growth of transformants. Genes encoding for antibiotics like ampicillin, tetracycline, chloramphenicol or kanamycin are considered to be useful selectable markers for E.coli.
3. Cloning Sites – The cloning vector should contain a single recognition site for the restriction enzymes in order to link the alien DNA. The presence of more than one recognition sites generates several fragments and complicates the cloning process.
4. It should have a high copy number so that we obtain many copies of the DNA linked to it
5. They should be able to replicate independently.
6. They should help easy linking of alien DNA.
B. DNA cannot pass through the cell membranes as it is a hydrophilic molecule. The cell membrane is made up of lipid bilayer which makes it difficult for the hydrophilic DNA molecule to pass through it.

Bacterial cells are made competent to take up recombinant DNA from the medium in the following ways-:
1. Treating bacteria with specific concentration of divalent cation such as calcium that results in an increase in the efficiency with which DNA is taken up by the bacterial cell. Recombinant DNA can then be forced into such cells by incubating them with the recombinant DNA on ice followed by placing them briefly at 42°C (heat shock), and again back on the ice.
Some other methods available for introduction of desired DNA are: 
1. Microinjection in which the recombinant DNA is directly injected into the nucleus of an animal cell.
 
2. Biolistics or gene gun method is suitable for plant cells, where cells are bombarded with high-speed micro-particles of gold or tungsten coated with DNA.

I. Restriction enzymes - Cutting of the desired gene at a specific location is attained by using restriction endonucleases. These enzymes are specialised to cut the fragment of DNA at specific locations. Each restriction endonuclease functions by ‘inspecting’ the length of a DNA sequence. Once it finds its specific recognition sequence, it binds to the DNA and cuts each of the two strands of the double helix at specific points in their sugar -phosphate backbones. Each restriction endonuclease recognises a specific palindromic nucleotide sequence (sequence of base pairs that reads same on the two strands when the orientation of reading is kept the same) in the DNA. Restriction enzymes cut the strand of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands. This leaves single-stranded portions at the ends.

II. Polymerase Chain Reaction - PCR is used to create multiple copies of the DNA being incorporated with molecular biology tools to obtain a higher copy of the desired gene. Two sets of chemically synthesised oligonucleotides and DNA polymerase are being used in vitro for the multiplication of the desired gene. 

The PCR  produces approximately billion copies of a gene in less than 20 minutes. Such higher number of the product is achieved by use of thermostable DNA polymerase (isolated from a bacterium, Thermus aquaticus. 

Components used during PCR - Template DNA, DNA polymerase, Primers and buffer. 

Steps of PCR – • 

Denaturation - The  DNA is denatured that is the strands are separated by heating the dsDNA to 95-degree celsius. This breaks hydrogen bonds that hold DNA strands together in the helix. •

Annealing- The mixture is cooled, this allows the primer to bind to their respective complementary sequence. •

 Extension- The mixture is then heated so that DNA polymerase can synthesise new strands.

The whole cycle is repeated to create multiple copies.