Beta-galactosidase activity is measured (absorbance units) for wild-type and a lacI- (constitutive) mutant in each medium.
What pattern in the lacI- mutant best supports the model of negative regulation by the lac repressor?
- Acheck_circle
High activity in all media including no sugar
- B
Activity only in lactose-containing media
- C
Activity only in glucose
- D
No activity in any medium
Explanation
Without functional repressor (lacI-), beta-galactosidase is expressed constitutively, regardless of inducer. High activity in all four media demonstrates that the wild-type repressor normally blocks transcription in the absence of lactose.