Arrange the given steps of PCR in correct sequence.
A. Extension
B. Annealing
C. Denaturation
D. Amplification
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → C, B, A, D
(C) Denaturation — comes first. The double-stranded DNA is heated to a high temperature, so its two strands separate. Each strand can then act as a template.
(B) Annealing — comes second. The mixture is cooled, and the two primers, which are short chemically made pieces of DNA, pair with the complementary regions of the separated strands.
(A) Extension — comes third. A thermostable DNA polymerase adds nucleotides to the primers and extends them, using the strand as a template. This forms new copies of the segment.
(D) Amplification — comes last. It is not a separate step but the result of repeating the three steps again and again. Each cycle doubles the DNA, so the segment is amplified about a billion times.
Note: A similar question was also asked in CUET (UG) 2026 on 26-05-2026 (Slot 1) and on 20-05-2026 (Slot 1), and in CUET (UG) 2025 on 02-06-2025 (Slot 2).