Practicing Success

Target Exam

CUET

Subject

Biology

Chapter

Molecular Basis of Inheritance

Question:

Observe the given picture and answer the following questions ?

 

What occurs in the presence of an inducer such as lactose or allolactose?

Options:

The repressor  is activated

The repressor is inactivated

RNA polymerase is inhibited

 

The operator region is blocked

Correct Answer:

The repressor is inactivated

Explanation:

The correct answer is Option (2) -The repressor is inactivated

The repressor of the operon is synthesised (all-the-time – constitutively) from the i gene. The repressor protein binds to the operator region of the operon and prevents RNA polymerase from transcribing the operon. In the presence of an inducer, such as lactose or allolactose, the repressor is inactivated by interaction with the inducer. This allows RNA polymerase access to the promoter and transcription proceeds . Essentially, regulation of lac operon can also be visualised as regulation of enzyme synthesis by its substrate.