Question

If a mutation occurred in the operator sequence of the lac operon, preventing the repressor from binding, what would be the most likely result?
Responses

Only one of the three lac genes would be expressed
Only one of the three lac genes would be expressed

Lactose-digesting enzymes would never be produced
Lactose-digesting enzymes would never be produced

The bacterium would die immediately
The bacterium would die immediately

Lactose-digesting enzymes would be produced constantly, regardless of lactose presence

Answer 1

Lactose-digesting enzymes would be produced constantly, regardless of lactose presence.

Reason: with the operator mutated so the lac repressor cannot bind, RNA polymerase can continuously transcribe the lac structural genes (lacZ, lacY, lacA), leading to constitutive expression. (Note: overall expression level can still be modulated by catabolite repression/CRP–cAMP in response to glucose.)