BIOS E-1a Lecture 12 110711 annotated

BIOS E-1a Lecture 12 110711 annotated - Lecture 12:...

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Lecture 12: Prokaryotic Gene Regulation Reading: Chapter 11 1
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2 ± Gene regulation refers to the ability of cells to control their level of gene expression ± Majority of genes regulated so proteins produce at certain times and in specific amounts ± Constitutive genes are unregulated and have essentially constant levels of expression
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Overview ± Benefits of gene regulation ² Conserves energy – proteins produced only when needed ² Ensures genes expressed in appropriate cell type and at the correct stage in development 3
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4 Gene regulation in prokaryotes ± Often used to respond to changes in the environment ± Escherichia coli and lactose example ± When lactose is not present, E. coli does not make a lactose permease (lactose transporter) and β -galactosidase ± When lactose is available, the proteins are made ± When lactose levels drop, the proteins are no longer made
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5 Lactose metabolism in bacteria
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6 Gene regulation can occur at different points ± Bacterial gene regulation ² Most commonly occurs at the level of transcription ² Or control rate mRNA translated ² Or regulated at protein or post-translation level
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7 Transcriptional regulation in bacteria ± Involves regulatory transcription factors ± Bind to DNA in the vicinity of a promoter and affect transcription of one or more nearby genes ± Repressors inhibit transcription ² Negative control ± Activators increase the rate of transcription ² Positive control
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8 Negative and positive transcriptional regulation
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9 ± Transcriptional regulation also involves small effector molecules ± Binds to regulatory transcription factor and causes conformational change ± Determines whether or not regulatory transcription factor can bind to DNA ± 2 domains in regulatory transcription factor that respond to small effector molecules ² Site where protein binds to DNA ² Site for small effector molecule
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10 Action of a small effector molecule on a repressor protein
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Operon ± Operon in bacteria is a cluster of genes under transcriptional control of one promoter ² Regulatory region called operator ± Transcribed into mRNA as polycistronic
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BIOS E-1a Lecture 12 110711 annotated - Lecture 12:...

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