Question

When a bacterial cell is present in an environment where both lactose and glucose are present, the glucose will be metabolized first and the lactose will be used when the stores of glucose have been depleted. How does a bacterial cell recognize the fact that glucose is present and turn off transcription of the lac genes even when lactose is present?(A) A CAP-cAMP complex is required for transcription, and its level is low when glucose is present.(B) The CAP binding site is activated.(C) Glucose is a repressor molecule.(D) The lac promoter binds glucose and shuts down the lac operon.

Answer 1

Option (A).

Step-by-step explanation:

Lac operon system in bacteria explains the lactose metabolism in the cell. The first operon system was discovered by Jacob and Monod. Operon may be defined as the cluster of genes that are transcribed as a single RNA unit.

The bacteria uses glucose if glucose and lactose are present in the media. The bacterial cell can recognize the glucose presence as CAP-cAMP complex are required for the process of transcription and the complex level is low in the presence of glucose. This way bacteria turns off transcription for lactose genes even when the lactose is present.

Thus, the correct answer is option (A).