Biology - Biotechnology - Principles and Processes Question with Solution | TestHub

Polymerase chain reaction (PCR) involves three main steps: denaturation, annealing, and extension.

During denaturation, the double-stranded DNA is heated to separate it into two single strands.

During annealing, the temperature is lowered to allow primers to bind to the complementary sequences on the single-stranded DNA.

During primer extension, the temperature is raised to the optimal working temperature of Taq polymerase (around $72^{\circ }\text{C}$). Taq polymerase synthesizes the new DNA strand by adding nucleotides to the $3^{\prime }$ end of the primers.

Therefore, Taq polymerase is actively involved only in the primer extension step.

Answer: Primer extension only