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LECTURE-34_Control of Prokaryotic Gene Expression

LECTURE-34_Control of Prokaryotic Gene Expression - Control...

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Control of Prokaryotic Gene Expression Campbell and Reece (7 th  Edition) Chapter 18: Pages 352- 358
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OBJECTIVES Describe a typical bacterial operon. Define the following terms: Promoter Operator Repressor Cis -acting element Corepressor Inducer
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OBJECTIVES Describe a repressible operon. Describe an inducible operon. Explain why the  typ  operon and the  lac  operon  can be examples of negative gene control. Describe the role of cAMP in the regulation of  the  lac  operon. Diagram the lac operon and the trp operon and  show how their structural genes are regulated.
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Cells respond to alterations in their environment by  turning on and turning off genes-very often families of  genes.
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Gene Regulation Is Necessary By switching genes off when they are not  needed, cells can prevent resources from being  wasted. There should be natural selection  favoring the ability to switch genes on and off. A typical human cell normally expresses about  3% to 5% of its genes at any given time. Cancer results from genes that do not turn off  properly. Cancer cells have lost their ability to  regulate mitosis, resulting in uncontrolled cell  division.
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Tryptophan biosynthesis is regulated at the transcriptional  level and also at the level of enzymatic activity. Negative feedback  inhibition. Enzyme 1 is  an allosteric enzyme.
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Two Levels of Metabolic Control Cells can regulate the activity of their enzymes. example: phosphofructokinase–1 (PFK-1). fast response. Cells can regulate the amount of enzyme  synthesized. transcriptional regulation. slower response.
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Regulation of Bacterial Gene Expression. The synthesis of messenger RNA for an enzyme  or a family of enzymes. DNA   RNA   Protein By what mechanism is the synthesis of RNA  regulated?
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The operator is a switch!
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