Which of the following is a correct sequence of steps in a PCR (Polymerase Chain Reaction)?
- Annealing, Denaturation, Extension
- Denaturation, Annealing, Extension
- Denaturation, Extension, Annealing
- Extension, Denaturation, Annealing
Answer
(2) Denaturation, Annealing, Extension
Solution
Each cycle of PCR has three steps:
1. Denaturation – the double-stranded DNA is separated by heating.
2. Annealing – the primers bind to the complementary sequences of the single strands.
3. Extension – thermostable DNA polymerase (Taq polymerase) extends the primers.
∴ Denaturation → Annealing → Extension
Answer: (2)