Question

A compound known as x-gal is widely used in molecular genetic research. when wild-type (normal) e. coli is grown on medium containing x-gal, the bacterial colonies turn blue. in contrast, when lacz mutants are grown on medium containing x-gal, the bacterial colonies remain their normal white colour. what is x-gal likely to be?

a. a compound chemically similar to galactose
b. a compound that cannot be transported into lacz mutants
c. a compound chemically similar to lactose
d. a compound that can only be transported into laca mutants
e. a compound chemically similar to glucose

Answer 1

X-gal is likely a compound chemically similar to lactose, which explains why wild-type E. coli turns bacterial colonies blue when grown on medium containing X-gal, while lacz mutants produce white colonies.

Step-by-step explanation:

X-gal is likely to be a compound chemically similar to lactose (option c). The reason for this is that wild-type E. coli, which has an intact lacZ gene, can metabolize X-gal and turn bacterial colonies blue. However, lacz mutants, which have a disrupted lacZ gene, cannot metabolize X-gal and therefore the colonies remain white.