What genes comprise the lac operon and how is it regulated?

What genes comprise the lac operon and how is it regulated?

• A. The lac operon operates independently of glucose levels and cAMP.
• B. The lacZ, lacY, lacA genes with promoter and operator; in absence of lactose the repressor inhibits transcription; in presence lactose allolactose binds repressor releasing it; CAP-cAMP enhances transcription when glucose is low.
• C. The lac operon consists of lacR, lacM, lacG with no promoter, and is always active.
• D. The lac operon is composed of lacZ, lacY, lacA with promoter and operator; the repressor is inactive in absence of lactose.

Answer: (B)