Q.45 Given below are two statements : One is labelled as Assertion (A) and the other is labelled as
Reason (R).

Assertion (A) :PCR is a technique to ampify large quantities of a specific DNA.

Reasons (R) :PCR technique involves the following steps; renaturation, denaturation and
synthesis.

In the light Of the above statements, choose the most appropriate answer from the options given
below :
(1)Both (A) and (R) are correct and (R) is the correct explanation of (A)
(2)Both (A) and (R) are correct but (R) is NOT the correct explanation of (A)
(3)(A) is correct but (R) is not correct
(4)(A) is not correct but (R) is correct

PCR DNA Amplification Steps: Renaturation Denaturation Synthesis Assertion-Reason Solved

PCR effectively amplifies specific DNA segments through repeated thermal cycling. Both assertion (A) and reason (R) are correct, but (R) uses non-standard terminology while accurately describing the core process, making option (2) the right choice.

Question Breakdown

Assertion (A) correctly states PCR’s primary function: amplifying targeted DNA from minute quantities to millions of copies via enzymatic replication.​
Reason (R) lists PCR’s three essential steps—denaturation (melting DNA strands), renaturation/annealing (primer binding), and synthesis/extension (Taq polymerase builds new strands)—though standard terminology uses “annealing” instead of “renaturation.”
(R) explains the mechanism behind (A)’s amplification but uses alternate naming, so it doesn’t perfectly “explain” in exam context.​

Option Analysis

• Option (1): Wrong—”Renaturation” differs from standard “annealing,” preventing (R) as direct explanation despite functional accuracy.​

• Option (2): Correct—Both statements true; PCR amplifies via these cyclic steps, but terminology nuance affects explanatory link.

• Option (3): Wrong—(R) correctly identifies PCR’s three-phase cycle despite naming variation; process fundamentally matches.​

• Option (4): Wrong—(A) precisely defines PCR’s biotechnological role in molecular diagnostics/research.​

PCR Cycle Steps