Regulation of Gene Expression in Prokaryotes

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Regulation of Gene Expression in Prokaryotes
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How Prokaryotes Regulate How Their Genes are
Expressed

• Possible points of regulation
• 1. Block transcription of the mRNA for that gene
• 2. Degrade mRNA as soon as it is made
• 3. Block translation at the ribosome
• 4. Degrade the new protein as soon as it is made
• 5. Inhibit the function of the protein

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The Rough Life of Intestinal E. coli

• You have cookies milk after school
• The E. coli in your intestines love to use
  glucose as an energy source
• Butyour mom forgot to buy cookies, so all you
  have is milk to drink
• Now, the E. coli needs to use lactose instead of
  glucose
• What now?

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E. coli can use Lactose

• But they need to gear up
• b-galactoside permease gets lactose into cell
• b-galactosidase splits lactose into glucose
  galactose
• b-galactoside transacetylase who knows?!
• These are inducible enzymes.
• Lactose is the inducer.

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The Lac Operon

• Operon consists of a promoter, operator, and at
  least 2 structural genes
• Promoter DNA on which RNA polymerase binds to
  begin making mRNA
• Operator DNA sitting between promoter and
  structural genes
• Structural genes DNA from which mRNA can be
  made

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Cookies and Milk(Glucose is PRESENT)
Glucose present
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Just Milk(Glucose is ABSENT Lactose is PRESENT)
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The Lac Operon

• Is an INDUCIBLE operon
• The operon is OFF until it is turned ON

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The Trp Operon
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The Trp Operon

• Is a REPRESSIBLE operon
• It is constantly on unless is it shut off
  (repressed).

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Gene Regulation in Eukaryotes
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Why Do Eukaryotic Cells Have to Regulate Their
Gene Expression?
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How Do Eukaryotes Regulate Gene Expression?

• 1. Extent of DNA packing

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How Do Eukaryotes Regulate Gene Expression?

• 2. Really tight packing X chromosome
  inactivation

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How Do Eukaryotes Regulate Gene Expression?

• 3. Regulation of Transcription Transcription
  Factors

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How Do Eukaryotes Regulate Gene Expression?

• 4. mRNA Processing Alternative Splicing

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Alternative Splicing