Arrange the following steps of 'Polymerase Chain Reaction' in a correct sequence.
(A) Annealing of primers
(B) Amplified DNA
(C) Denaturation of DNA
(D) Extension of primers
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (C), (A), (D), (B)
(C) Denaturation of DNA — first. Heat separates the two strands.
(A) Annealing of primers — second. The primers bind to their matching sequences on the single strands.
(D) Extension of primers — third. Taq polymerase adds nucleotides to the primers.
(B) Amplified DNA — last. Repeating the cycle many times gives about a billion copies.
Note: A similar question was also asked in CUET (UG) 2026 on 26-05-2026 (Slot 1), in CUET (UG) 2025 on 02-06-2025 (Slot 2) and on 30-05-2025 (Slot 1), and in CUET (UG) 2023 on 13-06-2023 (Slot 3), on 12-06-2023 (Slot 2), on 07-06-2023 (Slot 3) and on 31-05-2023 (Slot 3).
NCERT Extract:
Amplification of Gene of Interest Using PCR – “PCR stands for Polymerase Chain Reaction. In this reaction, multiple copies of the gene (or DNA) of interest is synthesised in vitro using two sets of primers (small chemically synthesised oligonucleotides that are complementary to the regions of DNA) and the enzyme DNA polymerase. The enzyme extends the primers using the nucleotides provided in the reaction and the genomic DNA as template. If the process of replication of DNA is repeated many times, the segment of DNA can be amplified to approximately billion times, i.e., 1 billion copies are made. Such repeated amplification is achieved by the use of a thermostable DNA polymerase (isolated from a bacterium, Thermus aquaticus), which remain active during the high temperature induced denaturation of double stranded DNA.”