Expand the following and mention one application of each:

(i) PCR (ii) ELISA

OR

(a) Mention the difference in the mode of action of exonuclease and endonuclease.

(b) How does restriction endonuclease function?

(i) PCR-Polymerase chain reaction is a molecular technique inwhich a gene or a segment of DNA can be amplified to obtain its several copies (around 1 billion copies).

Each cycle of PCR has three steps :
(a) Denaturation of DNA Strand
(b) Primer annealing
(c) Extension of primers
Use : It is used for the amplification of the gene of interest. Also used to identify many genetic disorder.
(ii) ELISA- (Enzyme Linked Immunosorbent Assay) is a molecular technique based on antigens-antibodies interaction to find out infectious diseases. Infection is detected by the presence of antigens like proteins or by the synthesis of antibodies against the infection.

This method is broadly used for the diagnosis of AIDS.

OR

(a) Exonucleases eliminate nucleotides from the ends of the DNA strand Endonucleases cut the DNA strand at specific positions within the DNA.

(b) Each restriction endonuclease discovers its specific palindromic nucleotide sequences in the DNA and cut at specific sites.

Once it discovers its specific recognition sequences than by binding to the DNA at these sites and cuts both the strands at specific points in their sugar-phosphate backbones.