Thinking of lactose operon regulation, what happens when E. coli is grown in medium with glucose...

Thinking of lactose operon regulation, what happens when E. coli is grown in medium with glucose and lactose?

Group of answer choices

neither Cap/cAMP activator nor LacI repressor are bound to a regulatory DNA sequence.

LacI repressor is bound to the OPERATOR sequence but Cap/cAMPactivator is not.

Cap/cAMP activator is bound to the CAP motif but LacI repressor is not.

both Cap/cAMP activator and LacI repressor are bound to the OPERATOR sequence.

Solutions

Expert Solution

lactose is an inducer of the lac operon.

the lac operon is inhibited by the lac repressor binding to the lac operator, in the presence of an inducer lac repressor is inhibited by the inducer so lac repressor cannot bind to the operator, so if lactose is present lac repressor cannot bind to the lac operator.

glucose inhibits the expression of lac operon by catabolite repression. CAP is catabolite activator protein it binds to the CAP binding site and recruit RNA polymerase to the lac promoter and increases the rate of transcription, for CAP to bind to DNA it has to be bound with cAMP, glucose decreases the levels of cAMP in the cell so cAMP-CAP complex cannot form so CAP cannot bind to the CAP site if glucose is present in the cell.

so the answer is a) neither Cap/cAMP activator nor LacI repressor are bound to a regulatory DNA sequence.

gladiator answered 1 year ago

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