question_answer

E.coli cells with a mutated z gene of the lac operon cannot grow in medium containing only lactose as the source energy because [CBSE PMT 2005]

A) In the presence of glucose, E.coli cells do not utilize lactose

B) They cannot transport lactose from the medium into the cell

C) The lac operon is constitutively active in these cells

D) They cannot synthesize functional betagalactosidase

Correct Answer: D

Solution :

The enzyme like lactase or -galactosidase which is formed in response to the presence of its called inducible enzyme.