Question

Which gene in lac operon is active all the time and its product is responsible to switch off the operon?
[0.7 mark]

• A. Promotor gene
• B. Operator gene
• C. Structural gene
• D. Regulator gene

Answer 1

The correct option is D Regulator gene

The repressor protein of the operon is synthesised all the time i.e., constitutively from the regulator gene (i gene). This repressor protein binds to the operator region of the operon and prevents RNA polymerase from transcribing the operon. Hence, regulatory gene in lac operon is active all the time.