Multiple Choice
The protein that binds to the operator of the lac operon to prevent transcription is encoded by which gene?
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15. Central Dogma & Gene Regulation
The Lac Operon
Multiple Choice
Which of the following statements accurately describes glucose repression in bacteria?
A
Glucose increases the activity of β-galactosidase by promoting lac operon transcription.
B
Glucose induces the lac operon by acting as an allolactose analog.
C
Glucose directly binds to the lac repressor, increasing its affinity for the operator.
D
Glucose represses the lac operon by decreasing cyclic AMP (cAMP) levels, which prevents activation of transcription.
Verified step by step guidance1
Understand that glucose repression in bacteria refers to the mechanism by which the presence of glucose inhibits the expression of certain operons, such as the lac operon, to prioritize glucose metabolism.
Recall that the lac operon is regulated by the lac repressor and by the catabolite activator protein (CAP), which requires cyclic AMP (cAMP) to activate transcription.
Recognize that when glucose levels are high, the intracellular concentration of cAMP decreases, reducing the binding of the cAMP-CAP complex to the promoter region of the lac operon.
Note that without the cAMP-CAP complex bound, RNA polymerase has a lower affinity for the lac operon promoter, leading to decreased transcription of genes like β-galactosidase.
Conclude that glucose repression works by lowering cAMP levels, thereby preventing activation of the lac operon transcription, rather than by directly interacting with the lac repressor or acting as an inducer.
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