Question

Given below are two statements :
Statement I: In the lac operon, the z gene codes for beta-galactosidase which is primarily responsible for the hydrolysis of lactose into galactose and glucose.
Statement II: In addition to lactose, glucose or galactose can also induce lac operon.
In the light of the above statements, choose the correct answer from the options given below :

• A. Statement I is true but Statement II is false
• B. Statement I is false but Statement II is true
• C. Both Statement I and Statement II are true
• D. Both Statement I and Statement II are false

Answer 1

Answer: (A)

Statement I is true but Statement II is false

Answer 2

Statement I: In the lac operon, the z gene does indeed code for β-galactosidase, the enzyme that hydrolyzes lactose into galactose and glucose. This statement is true.
Statement II: The lac operon is induced by the presence of lactose (or allolactose, a lactose isomer). The presence of glucose actually represses the lac operon, even if lactose is present. This phenomenon is called catabolite repression. Galactose doesn’t directly induce the lac operon; it’s the presence of lactose that matters. Therefore, statement II is false.