Question

Which of the phage genes are responsible for phage excision?

(a) xis gene

(b) int gene

(c) recA protein

(d) both xis and int gene

I got this question in an internship interview.

My doubt is from Bacteriophage Lambda topic in section Other Vector Systems for E of Genetic Engineering

Answer 1

The correct option is (d) both xis and int gene

The explanation is: As the level of cI genes fall, the repression of PR and PL genes is lifted up. Now phage genes are expressed and xis and int genes are expressed. These genes are responsible for causing phage excision.