Question

Describe how the lac operon operates, both in the presence and absence of an inducer in E.coli.

Answer 1

In absence of inducer, the repressor protein binds to the operator region and prevents RNA polymerase from transcribing the structural gene. Thus, the lac operon gene is inactivated.

Lac operon in presence of inducer binds with repressor protein and inactivates it. This allows RNA polymerase access to promoter and transcription proceeds.