Question

In the function of the lac operon in E. coli, the lac genes are transcribed in the presence of lactose because RNA polymerase binds to the operator. the repressor protein binds to the operator. allolactose binds to the repressor. CAP does not bind to the operator. of the absence of cAMP.

Answer 1

There are four parts of lac operon, but cAMP is just present when glucose is absent and just works in presence of lactose

Step-by-step explanation:

Lac operon is explained by a combination of compounds. There are two thing to have in mind before

First, the represor is always working, BUT is blocked by allolactose (rearrangement of lactose).

Second, the operon is enhanced in precence of cAMP and CAP protein. BUT, when glucose is present cAMP goes to work in glycolytic pathway and leaves lac operon without enhancement

Now, there are four arrengements possibles:

1. High lactose, low glucose: represor supressed so operon works and you get the transcript, no glucose then cAMP can enhance the operon

2.Low lactose, high glucos: as repressor is not supressed the operon does not work and you not get the transcript. cAMP does not mind

3.High lactose, high glucose: represor is supressed but the operon is not enhanced, you get few copies of the transcript

4.Low lactose, low glucose: as repressor is not supressed the operon does not work and you not get the transcript