Arrange the following steps involved in PCR in the correct sequence.
(A) Amplification
(B) Extension of primers
(C) Primer annealing
(D) Denaturation
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (D), (C), (B), (A)
(D) Denaturation — comes first. High temperature separates the double-stranded DNA into two single strands.
(C) Primer annealing — comes second. Two sets of primers, which are small chemically made pieces of DNA, bind to the complementary regions of the single strands. A primer can bind only to a single strand, so denaturation has to come before it.
(B) Extension of primers — comes third. A heat-stable DNA polymerase, taken from the bacterium Thermus aquaticus, adds nucleotides to the primers and copies the template.
(A) Amplification — comes last. It is the result of repeating the three steps many times. The DNA segment is multiplied to about a billion copies.
Note: A similar question was also asked in CUET (UG) 2026 on 26-05-2026 (Slot 2) and on 26-05-2026 (Slot 1), in CUET (UG) 2025 on 02-06-2025 (Slot 2), and in CUET (UG) 2023 on 31-05-2023 (Slot 3).