Identify P and R respectively in the following flowchart of PCR(polymerize chain reaction).

Heat , DNA polymerase.

The correct answer is Option (1) – Heat , DNA polymerase.

1. Step  is denaturation:
In denaturation, hydrogen bonds between the two strands of a double stranded DNA melts. Each separated strand acts as a template for the formation of new strands.

2. Step  is annealing:
In this step, synthetic oligonucleotides or primers bind to their complementary region, usually the gene of interest to be amplified. 

3. Step  is extension:
In this step, Taq DNA polymerase synthesises DNA by adding dNTPs to the free ends of the primers - forward and reverse.  This helps in synthesising complementary strands.

Polymerase chain reaction (PCR) : Each cycle has three steps: (i) Denaturation, (ii) Primer annealing;(iii) Extension of primers.