Question

Which of the following activity is not possible in the case of DNA polymerase I?

(a) 3’-5’ exonuclease

(b) 5’-3’ exonuclease

(c) 5’-3’ DNA synthesis

(d) 3’-5’ DNA synthesis

The question was posed to me in quiz.

My doubt stems from Polymerases in chapter Basics of Genetic Engineering of Genetic Engineering

Answer 1

Correct option is (d) 3’-5’ DNA synthesis

The explanation: DNA polymerase is having the ability to synthesize DNA strand in 5’-3’ direction but not in 3’-5’ direction. Also, it is having exonuclease activity in both the directions, which means that it can remove bases in either of the direction but can synthesize only in 5’-3’ direction.