Why is there X-gal used in the cloning medium?

Question

Quizplus · Accepted Answer

X-gal is a chromogenic substrate that turns blue in the presence of β-galactosidase, an enzyme encoded by the lacZ gene in the cloning vector. When a recombinant plasmid is inserted into the host bacteria, it disrupts the lacZ gene, resulting in white colonies that do not produce β-galactosidase and, thus, do not hydrolyze X-gal. Nonrecombinant plasmids maintain the integrity of the lacZ gene and generate colonies that produce β-galactosidase and, thus, hydrolyze X-gal, causing blue coloration. Therefore, X-gal is used for blue-white screening to distinguish between transformed and nontransformed bacteria.

Why Is There X-Gal Used in the Cloning Medium