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lecture16 - Gene Regulation We are now going to look at...

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Lecture 16 Lecture 16 Gene Regulation Gene Regulation We are now going to look at ways that genetics can be used to study gene regulation. The issue is how cells adjust the expression of genes in response to different environmental conditions. The principles of gene regulation were first worked out by Jacob and Monod studying the E. coli genes required for cells to use the sugar lactose as a nutrient. lactose lactose glucose + galactose (glucose-galactose) intracellular LacY LacZ (permease) ( β -galactosidase) log amount + lactose cell mass LacY or LacZ time The logic of the Lac Lac operon is that the proteins required to use lactose are only made when their substrate (lactose) is available. This prevents wasteful expression of enzymes when their substrates are notavailable. At first, scientists noted that lactose is both an inducer and substrate for the enzymes of the Lac operon and they therefore concluded that lactose was somehow acting as a template for the formation of the enzyme. Then compounds were discovered that could act as inducers but were not themselves substrates for the Lac Lac enzymes. The classic example of such a “gratuitous inducer” is IPTG IPTG , which is an effective inducer of LacZ LacZ expression but isn’t hydrolyzed by ß-galactosidase.
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