Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Polymerase chain reaction is used in DNA amplification. Reason (R): The ampicillin resistant gene is used as a selectable marker to check transformation. In the light of the above statements, choose the correct answer from the options given below:
Answer: (B) Both (A) and (R) are correct but (R) is not the correct explanation of (A). Answer: (b) Both (A) and (R) are correct but (R) is not the correct explanation of (A) Solution: Assertion is correct — PCR (Polymerase Chain Reaction) synthesises multiple copies of a gene/DNA of interest, i.e.
- A.Both (A) and (R) are correct and (R) is the correct explanation of (A)
- B.Both (A) and (R) are correct but (R) is not the correct explanation of (A)✓
- C.(A) is correct but (R) is not correct
- D.(A) is not correct but (R) is correct
Correct Answer
(B) Both (A) and (R) are correct but (R) is not the correct explanation of (A)
Solution & Explanation
Answer: (b) Both (A) and (R) are correct but (R) is not the correct explanation of (A) Solution: Assertion is correct — PCR (Polymerase Chain Reaction) synthesises multiple copies of a gene/DNA of interest, i.e. it is used for DNA amplification. Reason is also correct — the ampicillin resistance gene acts as a selectable marker to identify transformed cells. However, the two statements describe independent ideas: a selectable marker for transformation does not explain how/why PCR amplifies DNA, so (R) is not the correct explanation of (A). Hence (b). NCERT Reference: Ch 9, p.172, line(s) 16-17 — "PCR stands for Polymerase Chain Reaction. In this reaction, multiple copies of the gene (or DNA) of interest is synthesised"