Question

The enzyme Taq polymerase during PCR cycle is actually involved in which of the following steps?

• A. Both denaturation and annealing
• B. Both annealing and primer extension
• C. Annealing only
• D. Primer extension only

Hint:

Taq polymerase extends primers at about 72 degrees Celsius in the extension step only.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept
A PCR cycle has three steps: denaturation, annealing and extension.

Step 2: Role of Taq polymerase
Denaturation is done by heat and annealing is simple base pairing of primers, so no enzyme acts there.
Taq polymerase, a heat-stable enzyme from Thermus aquaticus, adds nucleotides to the primer only in the extension step.

Step 3: Conclusion
The enzyme works in primer extension only.

Final Answer:
Taq polymerase acts in primer extension only. \[ \boxed{\text{(D) }\text{Primer extension only}} \]