Question

From the given combinations of steps in PCR, identify the enzyme dependent step/s.

• A. Annealing and extension
• B. Annealing and denaturation
• C. Denaturation and extension
• D. Extension only

Answer 1

The Correct Option is D

Explanation of PCR Steps:

Denaturation (95°C):

• DNA strands separate (heat-dependent, no enzyme required)
• Non-enzymatic process

Annealing (50-65°C):

• Primers bind to template DNA
• Non-enzymatic process (hydrogen bonding)

Extension (72°C):

• Taq DNA polymerase adds nucleotides to synthesize new DNA strands
• Only enzyme-dependent step in PCR

Thus, the correct option is D: Extension only.

Answer 2

PCR Steps:

1. Denaturation (95°C): Heat separates DNA strands (no enzyme).
2. Annealing (50–65°C): Primers bind to template (no enzyme).
3. Extension (72°C): Taq polymerase synthesizes new DNA strands (enzyme-dependent).

PCR (Polymerase Chain Reaction) is a laboratory technique used to amplify (make many copies of) a specific segment of DNA. This powerful tool allows scientists to make millions of copies of a small DNA sample, making it easier to study, analyze, or manipulate the genetic material. PCR has widespread applications in fields like genetics, medicine, forensics, and research.

Why other options are incorrect:

• (A) Annealing is primer binding (enzyme not required).
• (B) Denaturation is heat-mediated.
• (C) Denaturation is non-enzymatic.

Correct Answer: (D) Extension only