Q41 / 200 · MHT CET - Medical 2026 (24 April Shift 1) · Biology
The enzyme Taq polymerase during PCR cycle is actually involved in which of the following steps?
- ABoth denaturation and annealing
- BBoth annealing and primer extension
- CAnnealing only
- Correct answerDPrimer extension only
Solution
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 $3'$ end of the primers.
Therefore, Taq polymerase is actively involved only in the primer extension step.
Answer: Primer extension only
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 $3'$ end of the primers.
Therefore, Taq polymerase is actively involved only in the primer extension step.
Answer: Primer extension only
Hence, the correct answer is option: 'D'.