2. (10 points) We have discussed how the lac operon (e Figureto both the CAP act

Question

2. (10 points) We have discussed how the lac operon (e Figureto both the CAP activator protein and the lac repressorlk the gene coding for the lac repressor so that now these all conditions. For these mutant cells, state whether the under the following situations and explain why in eac Q5-2) is controlled by You create cells that are mutant in cells lack the lac repressor under lac operon will be ON or OFF h case CAP. RNA binding binding site pol lymerase- start site for RNA synthesis (promoter) site operator -80 lacz gene -40 40 80 nucleotide pairs Figure Q5-2 A. B. In the presence of glucose and lactose 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

A. The presence of inducer releases lac repressor from the operator. Due to presence of glucose the level of cAMP is low because of which CAP remains inactive and cannot bind to DNA therefore transcription occurs at a low level.

B. lac repressor prevents transcription by remaining bound to the operator. Since glucose levels are high cAMP levels remain low which inactivates the CAP and cannot bind DNA.

C. Because of low level of glucose, the cAMP level will be high which will activate the cap and will bound to dna but the lac repressor will also be high and bound to the operator which will block the binding site for RNA polymerase thus preventing the transcription.

D. The presence of inducer religiousthe lac repressor from the operator. Sense glucose is absent cAMP levels are high which activates the CAP and bound to the DNA. CAP helps in binding RNA polymerase to the promoter which promotes transcription.

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