Name: 2. (10 points ) we have discussed how the lac operon (see Figure Q5-2) is

Question

Name: 2. (10 points ) we have discussed how the lac operon (see Figure Q5-2) is controlled by both the CAP th e gene coding for the lac repressor so that now these cells lack the lac repressor under all conditions. For these mutant ce activator protein and the lac repressor. You create cells that are mutant in lls, state whether the lac operon will be ON or OFF under the following situations and explain why in each case. RNA polymerase- (promoter) start site for RNA synthesis CAP- binding binding site site operator lacz gene -80 -40 40 80 nucleotide pairs Figure Q5-2 A. In the presence of glucose and lactose B. C. D. In the presence of glucose and the absence of lactose In the absence of glucose and the absence of lactose In the absence of glucose and the presence of lactose

Explanation / Answer

Lac operon contain operator promotor and a structural gene

A. lac operon active very low in presence of glucose and lactose

Because CAPis inactive and cannot cannot bind to DNA,

Because of the presence of inducer(allolactose), lac repressor is released from operator.

B. As CAP remain inactive in presence of glucose

Transcription will be very littile

C.Inactive

As lactose is very less. And glucose is very low

D. On

Lac repressor los ability to bind DNA, clearing way to RNA polymerase to transcribe the operon

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