The lactose operon is likely to be transcribed when
A) there is more glucose in the cell than lactose.
B) the cyclic AMP levels are low.
C) there is glucose but no lactose in the cell.
D) the cyclic AMP and lactose levels are both high within the cell.
E) the cAMP level is high and the lactose level is low.

Question

Quizplus · Accepted Answer

The lactose operon is regulated by both lactose and glucose levels. When glucose levels are high, transcription of the lactose operon is inhibited. However, when glucose levels are low, cyclic AMP (cAMP) levels are high and can bind to the CAP protein, allowing it to bind to the upstream promoter region in the lactose operon, thus enhancing transcription. Additionally, when lactose is present, it binds to the lac repressor protein and prevents it from binding to the operator region, allowing RNA polymerase to transcribe the genes in the operon. Therefore, the lactose operon is likely to be transcribed when both cyclic AMP and lactose levels are high within the cell. Choice D is the only option that accurately describes this scenario.

The Lactose Operon Is Likely to Be Transcribed When