Question

Select correct match with respect to lac-operon model?

• A.
  Active repressor + inducer → Inactive repressor
• B.
  Active repressor + corepressor → Inactive repressor
• C.
  Inactive repressor + inducer → Active repressor
• D.
  Inactive repressor + corepressor → Active repressor

Answer 1

The correct option is A

Active repressor + inducer → Inactive repressor
A repressible operon is the one in which transcription is reduced in the presence of a particular substance.

A substance that inhibits the expression of genes not by direct binding to DNA but instead indirectly regulates gene expression by binding to repressors is known as co-repressor.


The lac operon consists of one regulatory gene the i gene which codes for the repressor of the lac operon and three structural genes (z, y, and a). The repressor protein binds to the operator region of the operon and prevents RNA polymerase from transcribing the operon.

Active represser + inducer → Inactive repressor