prokGeneRegulation - Regulation of Gene Expression in...

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Regulation of Gene Expression in Prokaryotes Chapter 17
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Overview of prokaryotic regulation Genetic and molecular studies show that most regulation affects the initiation of RNA transcripts Studies of genes for lactose utilization Negative regulation – blocks transcription Positive regulation – increases transcription DNA binding proteins acting on RNA polymerase at promoter are main agents of regulation Attenuation of expression – tryptophan pathway Gene expression is fine tuned by premature termination of transcription
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Two general mechanisms of transcription regulation in prokaryotes
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The utilization of lactose by E. coli : A model system for gene regulation The presence of lactose induces expression of the genes required for lactose utilization Induction – stimulation of expression Inducer – molecule that stimulates expression Lactose – inducer of genes for lactose utilization Advantages of E. coli and lactose utilization system Culturing large numbers of bacteria allow isolation of rare mutants Lactose genes are not essential for survival (can use glucose as carbon source) Induction increases expression 1000-fold making mutant identification easy Color changes using β -galactosidase enzyme (e.g., OPNG, X-gal) make measurement of expression levels efficient.
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Coordinate repression and induction of three genes revealed by studies of lactose- utilization mutants Jacques Monod and Francois Jacob (Pasteur Institute in Paris) Proposed Operon Theory Operon Theory of gene regulation Single signal can simultaneously regulate expression of several genes that are clustered together on a chromosome and involve the same process Because genes are clustered, they are transcribed together as single mRNA Clusters of genes are called Operons
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Complementation analysis of mutants identifies lactose utilization genes Monod et al. isolated many Lac - mutants unable to utilize lactose
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This note was uploaded on 12/17/2009 for the course BIO 2354 taught by Professor Brockett during the Spring '08 term at Georgia Institute of Technology.

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prokGeneRegulation - Regulation of Gene Expression in...

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