LECTURE-34_Control of Prokaryotic Gene Expression

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

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Unformatted text preview: Control of Prokaryotic Gene Expression Campbell and Reece (7 th Edition) Chapter 18: Pages 352- 358 OBJECTIVES Describe a typical bacterial operon. Define the following terms: Promoter Operator Repressor Cis-acting element Corepressor Inducer 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. Cells respond to alterations in their environment by turning on and turning off genes-very often families of genes. 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. 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. Two Levels of Metabolic Control Cells can regulate the activity of their enzymes. example: phosphofructokinase1 (PFK-1). fast response. Cells can regulate the amount of enzyme synthesized. transcriptional regulation. slower response. 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? The operator is a switch!...
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This note was uploaded on 03/31/2009 for the course BIO 202 taught by Professor Dean during the Spring '08 term at SUNY Stony Brook.

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

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