AP BIOLOGY

Detailed explanation-1: -The colonies formed by non-recombinant cells, therefore appear blue in color while the recombinant ones appear white. The desired recombinant colonies can be easily picked and cultured. Isopropyl -D-1-thiogalactopyranoside (IPTG) is used along with X-gal for blue-white screening.

Detailed explanation-2: -Blue colonies contain a plasmid, however they are producing ß-galactosidase (evident by their ability to convert X-GAL into a blue precipitate) indicating that they do not contain inserts.

Detailed explanation-3: -Reason: Presence of insert results in inactivation of enzyme beta-galactosidase known as insertional inactivation.

Detailed explanation-4: -Blue colonies therefore show that they may contain a vector with an uninterrupted lacZ (therefore no insert), while white colonies, where X-gal is not hydrolyzed, indicate the presence of an insert in lacZ which disrupts the formation of an active -galactosidase.

Detailed explanation-5: -Any colony containing the plasmid (and therefore the functioning -galactosidase gene) will turn blue, a result of the -galactosidase activity. This is called -complementation.