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

The Correct Option is A

To determine the correct answer, we need to analyze both statements regarding the lac operon, a classic example in genetics that illustrates gene regulation in prokaryotes, specifically in Escherichia coli.

• 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."

This statement is true. In the lac operon, the z gene indeed encodes an enzyme called beta-galactosidase. This enzyme is crucial for breaking down lactose, a disaccharide sugar, into its monosaccharide components—galactose and glucose. This hydrolysis is a necessary step for the bacteria to utilize lactose as a source of energy.

• Statement II: "In addition to lactose, glucose or galactose can also induce lac operon."

This statement is false. The lac operon is primarily induced by the presence of lactose, which acts as the inducer by binding to the repressor and thereby allowing transcription. However, glucose actually represses the lac operon through a mechanism known as catabolite repression. When glucose is present, the lac operon is not induced, as the cell prefers to use glucose directly. Galactose does not induce the lac operon; it is the breakdown product of lactose hydrolysis, not an inducer.

Therefore, after examining both statements, we can conclude:

• The correct answer is: Statement I is true but Statement II is false.