Question at position 6 E.coli grown with the only nutrient as lactose will have what bound to it’s lac operon?CRP-cAMP onlyRepressor and inducer.CRP onlyrepressorinducerClear my selection

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Question at position 6  E.coli grown with the only nutrient as lactose will have what bound to it’s lac operon?CRP-cAMP onlyRepressor and inducer.CRP onlyrepressorinducerClear my selection

BlackTom AI · Accepted Answer

Question restated: When E. coli is grown with lactose as the only nutrient, what is bound to its lac operon?

Option 1: CRP-CAP complex bound to lac promoter as CRP-cAMP. This option reflects the fact that in the absence of glucose, cyclic AMP (cAMP) levels rise and form a complex with CRP (also called CAP). This CRP-cAMP complex binds near the lac operon and promotes transcription by aiding RNA polymerase binding, thus helping activate the operon in the presence of an inducer like lactose. This is consistent with catabolite activation when glucose is scarce.

Option 2: Repressor and inducer. The lac repressor binds to the operator when lactose is absent or in low levels of the inducer. However, in the presence of lactose, allolactose (the inducer) binds to the repressor and inactivates it, causing the repressor to dissociate from the operator. Since lactose is present, the repressor is not bound, so this option is incorrect.

Option 3: CRP only. While CRP-cAMP is important for activation, it does not act alone. The lac operon requires the CRP-cAMP complex to assist transcription, but it is not simply CRP bound without the cAMP partner. So this option is incomplete.

Option 4: Repressor. As explained, the lactose-derived inducer allolactose binds the lac repressor and prevents its binding to the operator. Therefore, the repressor is not bound under these conditions, making this option incorrect.

Option 5: Inducer. Allolactose would act as the inducer to inactivate the lac repressor, but the question asks what is bound to the lac operon. The inducer is not a steady bound factor; it interacts with the repressor to relieve repression. Since the repressor is not bound in this lactose-present condition, simply labeling inducer as bound is misleading, so this option is not accurate for what is bound to the operon.

In summary, the combination that accurately describes what is bound to the lac operon under these conditions is the CRP-cAMP complex, which activates transcription in the presence of lactose when glucose is not present.

Question at position 6 E.coli grown with the only nutrient as lactose will have what bound to it’s lac operon?CRP-cAMP onlyRepressor and inducer.CRP onlyrepressorinducerClear my selection

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