Beta-galactosidase activity (lac operon) was measured in E. coli grown under combinations of glucose and lactose.
The pattern is consistent with which regulatory logic?
- Acheck_circle
Lac operon is induced by lactose only when glucose is absent.
- B
Lactose alone is sufficient to induce regardless of glucose.
- C
The operon is constitutive.
- D
Glucose induces the operon when lactose is present.
Explanation
High activity only when glucose absent and lactose present reflects dual control: cAMP-CAP activation requires low glucose; allolactose inactivates the lac repressor.