Chapter 15 Control of Gene Expression

Chapter 15 Control of Gene Expression - Chapter 15 Control...

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Chapter 15 Control of Gene Expression I. A Cascade of Proteins and Cancer A. Cyclin and cdc2 are proteins that initiate cell division. B. In cancer cells these proteins are not destroyed after a division cycle; therefore, the cells keep dividing without controls. II. The Nature of Gene Control A. Because all cells in your body have the same genetic instructions, only a relatively small number of genes are active at any given time in any given tissue (example: only red blood cells activate hemoglobin genes). B. Control Agents and Where They Operate 1. Transcriptional controls depend on two types of regulatory proteins: a. Repressor proteins prevent RNA polymerases from binding to DNA—negative control. b. Activator proteins enhance binding of RNA polymerases—positive control. 2. In vertebrates, hormones are agents of control. 3. Some control agents bind to promoter sequences at the start of a gene; others bind to the operator sequences between the promoter and the start of a gene. C. Gene controls operate in response to chemical changes within the cell or its surroundings. III. Gene Control in Prokaryotes
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This note was uploaded on 01/04/2012 for the course BSC BSC1005 taught by Professor Orlando,rebecca during the Fall '10 term at Broward College.

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Chapter 15 Control of Gene Expression - Chapter 15 Control...

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