Question

If the nick is at 5’ end of the mismatch which of the following will be recruited?

(a) Rec J

(b) Ruv D

(c) Exonuclease I

(d) Exonuclease X

This question was posed to me in unit test.

The question is from Repair of DNA Damage: MMR, BER in portion DNA Mutation, DNA Repair, Transposable Elements of Cytogenetics

Answer 1

Correct answer is (d) Exonuclease X

To explain: Rec J is an exonuclease which is also known as exonuclease VII. It is responsible for chewing the DNA from 5’ to 3’ direction. While exonuclease I and X chew from 3’ to 5’ direction which will not be of much use in this case.