Question

In the lac operon, what are the likely effects on operon gene transcription of the mutations identified below? Mutation of the CAP binding site of the lac promoter.

1) Transcription is blocked.
2) Transcription is constitutive.

Answer 1

A mutation in the CAP binding site of the lac operon would likely reduce the efficiency of operon gene transcription due to a disruption in the CAP-cAMP complex's ability to bind and induce transcription under low glucose conditions.

Step-by-step explanation:

In the lac operon, a mutation in the CAP binding site can impact the regulation of operon gene transcription. Normally, when glucose levels are low, cAMP levels rise and bind to the CAP, activating it. This CAMP-CAP complex binds to the promoter region of the lac operon and induces transcription when glucose is low and lactose is present. If a mutation occurs in the CAP binding site, the CAMP-CAP complex would not bind successfully, potentially reducing the efficiency of transcription initiation. This doesn't necessarily block transcription since the operon can still be activated without CAP when lactose is present, but maximal activation under low glucose conditions would be disrupted, leading to a decrease in the lac operon transcription when it might be needed.