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Unformatted text preview: Lecture 23 How are genes regulated? A. Gene regulation in prokaryotes- We are eukaryotes, so we have a lot of cells, but how do these cells differentiate?- One of the reasons genes need to be regulated it so cells can be differentiated Some genes are turned on and some are turned off Once cells are differentiated it is hard to go back, which is why stem-cells kick ass (they havent been programmed yet Prokaryotes dont need to differentiate, but they need to save energy so all of their enzymes arent turned on all the time (us too) This is probably the most studied area 1. Constitutive genes- These are always turned on because the products are always needed- Other genes arent always turned on 2. Beta-galactosidase a. Escherichia coli- Found in the intestinal tract- Single-cells and small (rods)- Han produce beta-galactoside, which break down beta-galactosides (lactose) Glucose + galactose- If you dont drink milk and you examine this ecoli, it may have 3 molecules of B-G in it (it is never shut off completely, but it may come down close to zero) but if you drink milk, the ecolis enzyme will shoot up to 3000 b. Lactose c. C. galactose permease Gets lactose through cell membrane d. Galactoside transacetylase...
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- Fall '07