Question

The cI function can be scanned in order to check whether the recombinants are present or not. Which of the following doesn’t hold true?

(a) The cI protein is required for the formation of lysogen

(b) The plaques formed are turbid in the case if the cI gene is active

(c) The plaques formed are clear in the case if the cI gene is inactive

(d) hflA mutant host reduces the amount of cII stability

This question was addressed to me in an interview for job.

This interesting question is from Cloning in Lambda in section Other Vector Systems for E of Genetic Engineering

Answer 1

Right answer is (d) hflA mutant host reduces the amount of cII stability

Easiest explanation: The cI protein is required for the formation of lysogen to take place. The plaques formed are clear in the case if cI is inactive and turbid in the case if cI is active. hflA (high frequency of lysogenization) mutant hosts is used for enhanced screening. It is so because it increases the amount of cII stability and thus consequently lysogenization is taking place efficiently.