Question

If genomic DNA has been inserted instead of the plasmid, what will happen?

(a) It would lead to inactivation of lacZ gene

(b) The X-gal substrate would be broken down

(c) The colonies formed are blue in colour

(d) The lacZ gene would be intact

The question was asked during an interview.

This question is from Cloning using a Simple Plasmid and Alpha Complementation in division Simple Cloning of Genetic Engineering

Answer 1

Right option is (a) It would lead to inactivation of lacZ gene

The best explanation: If genomic DNA is inserted instead of the plasmid the lacZ gene would be inactivated. The X-gal substrate won’t be broken down and thus the colonies formed would be white or off-white.