Write the principle of PCR technic mention the rule of molecular dighnosis?

Polymerase chain reaction, orPCR, is a technique to make many copies of a specific DNA region in a test tube.It involves use of Taq polymerase which remains stable even at very high temperature and requires two DNA primers which are designed specifically for DNA region which is to be amplified.
There are 3 steps repeated:
1. Denaturation to unwind DNA (90-95 C)
2. Annealing of Primers to template strands (45-55 C, Variable temperature)
3. Extension: New deoxynucleotides are added by taq polymerase complementary to template DNA strand. (72 C)

In PCR, the reaction is repeatedly cycled through a series of temperature changes, which allow many copies of the target region to be produced.NO of copies formed can be calculated by 2^n where n is no of cycles.