Identify the step, not involved in polymerase chain reaction.

The correct answer is Option (3) → Phosphorylation

In the polymerase chain reaction (PCR) each cycle has three steps. They are repeated about 30 times to make about a billion copies of the DNA.

(1) Annealing — A step of PCR. The primers bind to their complementary sequences on the single strands.

(2) Denaturation — A step of PCR. High temperature separates the two strands of the DNA.

(3) Phosphorylation — Not a step of PCR. It means adding a phosphate group to a molecule. No such step is part of the cycle.

(4) Extension — A step of PCR. The heat-stable Taq polymerase extends each primer by adding nucleotides.