Question

How can one end be protected from the action of Exonuclease III, so that the molecule is not shortened from both the ends?

(a) By using Phosphorothioate nucleotide analogue

(b) By making both the ends double stranded in nature

(c) By labelling one end with a radioactive compound

(d) By increasing the time of exposure of the DNA molecule to the enzyme

The question was asked during an online exam.

This key question is from Exonucleases topic in chapter Basics of Genetic Engineering of Genetic Engineering

Answer 1

Correct answer is (a) By using Phosphorothioate nucleotide analogue

To explain I would say: Phosphorothioate nucleotide analogues are used to replace some of the nucleotides at the ends with it. It doesn’t allows the action of the enzyme on it and thus the molecule won’t be shortened from that end on which replacement is done.