Arrange the given steps involved in Polymerase Chain Reaction in correct sequence?
(A) Annealing
(B) Extension
(C) Denaturation
(D) Amplification
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (C), (A), (B), (D)
(C) Denaturation — first. The double-stranded DNA is heated to a high temperature. The two strands separate, so each can act as a template.
(A) Annealing — second. The mixture is cooled. The two primers bind to their complementary regions on the single strands. Primers are short, chemically made pieces of DNA.
(B) Extension — third. The heat-stable DNA polymerase (Taq polymerase) adds nucleotides to the primers and copies the template strands.
(D) Amplification — last. Amplification is not a separate step of one cycle. It is the result of repeating the three steps many times (about 30 cycles). The DNA doubles in each cycle and reaches about a billion copies.
Note: The same question was also asked in CUET (UG) 2025 on 30-05-2025 (Slot 1), and a similar question in CUET (UG) 2026 on 26-05-2026 (Slot 2) and on 20-05-2026 (Slot 1), and in CUET (UG) 2023 on 15-06-2023 (Slot 1), 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 – “… 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.”
