11. Explain briefly :
Polymerase Chain Reaction (PCR)- The molecular technique to amplify a gene and obtain its several copies is referred to as PCR. The process of PCR has certain requirements i.e. a thermostable enzyme called Taq polymerase ( obtained from Thermus aquaticus), primers ( short stretches of DNA ), dNTPs, a template strand etc. The process of PCR takes place in three steps.
1. Denaturation- The double-stranded DNA helix is opened up by breaking their H-bonds at high temperature.
2. Annealing- The primers are allowed to hybridise to complementary regions of DNA. This step takes place at 45-55 C temperature.
3. Extension- The primers are extended with the help of Taq polymerase enzyme and the cycle is repeated several times to obtain the desired number of copies.