The lac operon is regulated by both a positive transcriptional control system and a negative transcriptional control system. Under what conditions will both systems operate to stimulate transcription of the lac operon?

Question

Quizplus · Accepted Answer

The lac operon is activated by low glucose levels and the presence of allolactose. Low glucose levels stimulate the positive transcriptional control system by increasing the concentration of cyclic AMP (cAMP), which binds to and activates the catabolite activator protein (CAP), which then binds to the promoter of the lac operon and stimulates transcription. The negative transcriptional control system is inactivated by the presence of allolactose, which binds to and inhibits the lac repressor, allowing transcription to occur. Therefore, both systems will operate to stimulate transcription when there is low glucose and high allolactose, as is the case during lactose utilization.

The Lac Operon Is Regulated by Both a Positive Transcriptional