Question

Which of the following mutation will lead to AT->GC transition?

(a) Nitrous acid acting on A

(b) Nitrous acid on C

(c) Hydroxylation of C

(d) Methylation of G

I got this question in an interview.

The origin of the question is DNA Mutation topic in division DNA Mutation, DNA Repair, Transposable Elements of Cytogenetics

Answer 1

The correct option is (a) Nitrous acid acting on A

Explanation: All options other than oxidation of A by nitrous acid lead to GC->AT transition. Nitrous acid converts A to Hypoxanthine that in place of pairing with T pairs with C. Thus, it leads to AT->GC transition.