Question: 117. Which of the following is a correct sequence of steps in a PCR (Polymerase Chain Reaction) ?
(1) Denaturation, Annealing, Extension
(2) Denaturation, Extension, Annealing
(3) Extension, Denaturation, Annealing
(4) Annealing, Denaturation, Extension
Answer: Option (1)
Explanation:
PCR is a technique used to amplify a specific segment of DNA.
The first step is denaturation, in which double-stranded DNA is separated into single strands by heating.
The second step is annealing, where short DNA primers bind to their complementary sequences on the single-stranded DNA.
The third step is extension, during which a thermostable DNA polymerase synthesizes new DNA strands.
This cycle is repeated many times to produce millions of copies of the target DNA.
Hence, the correct sequence is denaturation, annealing, and extension.