6. Regluation_Study_Guide.pptx - Unit 6.Regulation Controlling all these genes Part 1 Gene Regulation in Bacteria Featuring E coli as everyones favorite

6. Regluation_Study_Guide.pptx - Unit 6.Regulation...

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Unit 6.Regulation Controlling all these genes
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Part 1. Gene Regulation in Bacteria Featuring E. coli as everyone’s favorite model
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Concepts for Study There are many steps in gene expression (RNA Synthesis to Protein Synthesis) and regulation can occur at any one of them Genetic and molecular studies show that most regulation affects the initiation of RNA transcripts Lac paradigm Attenuation of expression: Gene expression is fine tuned by premature termination of transcription Trp paradigm Global regulatory mechanisms: Expression of different sets of genes dispersed around the chromosome is coordinated.
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Recall Transcription (RNA synthesis) Do you remember the events at each stage? Initiation Elongation Temination
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Transcription is coupled to Translation (Protein Synthesis) Recall: Translation in bacteria starts before transcription ends Initiation sites for translation signal ribosomes to bind near 5’ end of mRNA while downstream transcription is still occurring Polycistronic mRNAs (several genes are transcribed in one long mRNA) lead to the translation of several genes at the same time from one mRNA transcript
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At what point are genes regulated? Discuss. Where do you think the “decision” is made for a gene product to be produced or not? Transcription? Translation? What step?
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Actually… The regulation of gene expression can occur at many steps Binding of RNA polymerase to promoter Shift from initiation to elongation Release of mRNA at termination Posttranscriptional stability of mRNA Efficiency of ribosomes to recognize translation initiation sites Stability of polypeptide product
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Bacterial Gene Organization Before we can understand how genes are regulated, let’s learn more about the structure of the gene beyond the promoter elements we’ve discussed
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Bacterial Gene Organization Bacteria are efficient and organized Operons are clusters of genes that are involved in the same process This clustering means a single signal can simultaneously regulate expression of several genes
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Bacterial Gene Organization Because genes are clustered, they are transcribed together as single mRNA Jacques Monod and Francois Jacob (Pasteur Institute in Paris, 1961) proposed Operon Theory of gene regulation, modeled by the Lac operon
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The utilization of lactose by E. coli: A model system for gene regulation The Lac operon contains genes that are needed for lactose utilization If lactose is present in the media, should E. coli turn these genes on or off? If lactose is not present, should they be on or off?
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Your text has the same figure, just smaller
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Some gene regulation terms Induction: Gene expression occurs (protein product detectable), stimulated by a specific signal Inducer: Molecule that stimulates induction Repressor: Molecule that shuts down induction
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Structure of an Inducible gene *Operons may contain several genes, controlled by a single repressor and/or an inducer
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