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. Why is this method of selection referred to as "insertional inactivation"?

(A) When the foreign gene is inserted within alpha - galactosidase gene, the enzyme alpha - galactosidase gets inactivated. The bacteria are grown on a chromogenic substrate. The non-recombinants will produce blue-colored colonies while the recombinants will produce white / colorless colonies because of the inactivation of the gene alpha-galactosidase. (b) Insertional inactivation is the loss of the function of a gene such as alpha-galactosidase gene in plasmid due to insertion of foreign DNA / transgene within it. This tool is used to select recombinants.