(a) A recombinant vector with a gene of interest inserted within the gene of α-galactosidase enzyme, is introduced into a bacterium. Explain the method that would help in selection of recombinant colonies from non-recombinant ones.

(b) Why is this method of selection referred to as “insertional inactivation”?

a. Chromogenic substrate is used to identify recombinants and non-recombinants. The bacteria are grown in a medium with chromogenic substrate. Recombinants show no blue coloration while non-recombinants show blue coloured colonies.

b. This method is called “insertional inactivation” because the insertion of recombinant-DNA within the coding sequence β-galactosidase enzyme site results into inactivation of the enzyme.