NEETZoologyMolecular Basis of Inheritance
In the lac operon of E. coli, the repressor protein synthesized by the i gene exerts its regulatory effect by:
Options
- Abinding to the promoter region to prevent RNA polymerase from attaching.
- Bbinding to the operator region to prevent RNA polymerase from transcribing the structural genes.
- Cbinding directly to the structural genes to prevent their translation into enzymes.
- Dbinding to the inducer molecule to prevent the initiation of transcription.
Correct answer
B. binding to the operator region to prevent RNA polymerase from transcribing the structural genes.
Step-by-step solution
The i gene synthesizes the repressor protein constitutively. This repressor protein binds specifically to the operator region of the operon. This physical binding creates an obstacle that prevents RNA polymerase (which binds to the adjacent promoter) from accessing and transcribing the structural genes. Option 1 is incorrect because RNA polymerase binds to the promoter, not the repressor. Option 3 is incorrect because the repressor targets the operator, not the structural genes themselves, and it inhibits transcrip