Chapter14Sum07

Chapter14Sum07 - Trace the making of a eukaryotic protein...

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Trace the making of a eukaryotic protein starting with DNA and ending with the protein released outside the cell.
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DNA mRNA protein activated protein
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Controls Over Genes Chapter 14 Fruit fly chromosome
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Gene Control in Prokaryotes No nucleus separates DNA from ribosomes in cytoplasm When nutrient supply is high, transcription is fast Translation occurs even before mRNA transcripts are finished
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E. Coli and Lactose
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regulatory gene operator operator promoter gene 1 gene 2 gene 3 Fig. 14-3a, p.209 Lac Operon Codes for repressor protein Code for enzyme 1, 2, and 3 which are involved in lactose breakdown Lac Operon: one example of negative gene control in prokaryotes
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If milk (lactose) is present, then the bacteria should make enzymes 1, 2, and 3 which “break down” lactose. If no milk (lactose) is present, it would be a waste of energy to make proteins 1, 2, and 3 which would have no substrate and no use in the cell. Consider bacteria that live in the guts of animals
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repressor protein In the absence of lactose , the repressor protein binds to two operators in DNA. It makes the DNA loop out in a way that blocks RNA polymerase from binding to its promoter BLOCKS TRANSCRIPTION operator in DNA operator in DNA Fig. 14-3b, p.209 Repressor protein operators promoter Gene 1
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Gene expression in prokaryotes Lac operon If lactose is not present, then transcription is OFF.
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lactose When lactose is present , some is converted to allolactose that binds to the repressor and alters the repressor’s shape. The altered repressor protein can’t bind to operators, so RNA polymerase is free to transcribe the operon genes 1, 2, and 3. allolactose translation into polypeptide chains for the three enzymes mRNA RNA polymerase operator operator gene 1 promoter Fig. 14-3c, p.209
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If lactose is present, then transcription is ON.
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What makes the cells in our body different from each other? The reason your skin cells have different
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Chapter14Sum07 - Trace the making of a eukaryotic protein...

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