Question

The restriction endonuclease is having a defence mechanism in the bacterial system against foreign DNA such as viruses. But how it is able to protect its own DNA?

(a) By methylation of bacterial DNA by restriction enzyme

(b) By methylation of foreign DNA by restriction enzyme

(c) By phosphorylation of bacterial DNA by restriction enzyme

(d) By phosphorylation of foreign DNA  by restriction enzyme

This question was posed to me in an online quiz.

This intriguing question comes from Restriction Endonuclease & Phosphatases in portion Basics of Genetic Engineering of Genetic Engineering

Answer 1

The correct option is (a) By methylation of bacterial DNA by restriction enzyme

Explanation: The bacterial DNA is methylated by restriction enzyme and thus now it is not recognized by the restriction endonuclease. Thus methylation prevents the restriction endonuclease from cutting its own DNA.