Question

You are inserting your gene of interest into the Lac Z gene in a plasmid also containing a tetracycline resistant gene. You plate your transformed bacteria on media containing tetracyline and X-gal (the LacZ substrate that can form a blue dye). What results would indicate a clone with recombinant plasmids?

Answer 1

A white colony in tetracyline plates

Step-by-step explanation:

Beta-galactosidase (also known as beta-gal or β-gal), will not be produced if a gene was cloned into the Lac Z gene. It is because β-galactosidase is produced by the activation of the lacZ gene, and thereby β-gal can not be produced in the absence of this lac operon. In consequence, X-gal will not be hydrolyzed by the β-gal enzyme in a reaction that releases a blue pigment, and thus the colony will be white. In gene cloning, X-gal enables to determine whether a cell is expressing a functional β-gal enzyme, which is known as the "blue/white screening method".