Question

Escherichia coli with mutated z gene of lac operon cannot grow in medium containing only lactose as the source of energy because
A. Lac operon is constitutively active in these cells
B. They cannot synthesise functional beta-galactosidase
C. In the presence of glucose, Escherichia coli cannot utilise lactose
D. The bacterium cannot transport lactose from the medium into the cell

Answer 1

Correct Answer - B
`**" "`the z gene codes for beta-galactosidase (`beta`-gal), which is primarily respondibel for the hydrolysis of the disaccharide, lactose into its monomeric units, galactose and glucose.
`**" "`Escherichia coli with mutated z gene of lac operon cannot grow in medium containing only lactose as the source of energy because they cannot synthesis functional galactosidase.