Tho gene machine program shows you what happens when lactose is present in E. co

Question

Tho gene machine program shows you what happens when lactose is present in E. coti, and how the Lie operon is under negative control. However, the Lie operon is also under positive control from a protein called CRP. cAMP Receptor Protein. I he absence of the Lie repressor is essential hut not sufficient for effective transcription of the lac operon. RNA polymerase also depends on the presence of CRP. I.ikc the Lie repressor, which can hind to the ON A anti lactose. CRP also has two types of binding sites: a site that types 01 minting sites: a site that binds to the DNA near the promoter, and a site that binds to cAMP. c AMP (cyclic AMP) is a signal molecule w hose concentration in the cell is inversely proportional u> that ol glucose. cAMP is created from ATP by the enzyme adcnylyl cyclase, and is used as an intercellular signaling molecule to regulate sugar and lipid metabolism. When glucose is present. coti will always prefer to metabolize glucose, but when glucose levels are low CAMP Jewels will begin to increase and the CRP-cAMPcomplex levels will rise. he ( RP-cAMP complex w ill hind to the CRP binding site on the DNA upstream of the expression of the Lie operon genes by enhancing the binding of RNA pohmerase to the promoter sequence. Using ,hc figure above, explain w hy RNA polymerase is not bound to the promoter when both lactose and glucose is present. Lxplnin why the lac operon sfaiiis is Oi l- when neither glucose or lactose is present, even though K.N'A polymerase is hound to the promoter. The lac operon is under both negative (the repressor) and positive (CRP) control. Why do you think this is? Why would this be beneficial?

Explanation / Answer

The main advantage is, this mechanism help the bacterial cells as an economical means to restrict the expression of the structural genes which are necessary.

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