Question

The correct order of steps in PCR is:
(A) Annealing,
(B) Denaturation,
(C) Extension

• A. (B), (A), (C)
• B. (A), (B), (C)
• C. (B), (C), (A)
• D. (C), (A), (B)

Hint:

Denaturation helps separate the two strands of DNA by breaking the hydrogen bonds, annealing helps the primer bind to its complementary sequence and extension helps in adding of nucleotides by DNA polymerase.

Answer 1

The Correct Option is B

PCR (Polymerase Chain Reaction) is a technique used to amplify DNA by three
main steps:
• Denaturation: The DNA is heated to 95°C, causing the double stranded DNA molecule to separate into two single strands.
• Annealing: The temperature is lowered to 50-65°C to allow the primers to bind to the complementary sequences of the DNA strands.
• Extension: The temperature is raised to 72°C (optimum temperature for Taq DNA Polymerase) to allow DNA polymerase to synthesize new DNA strands by adding nucleotides to the primers.
These steps are repeated in cycles to amplify specific regions of the DNA. The correct order is
therefore Denaturation >Annealing > Extension.