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Regulation of Gene Expression

Regulation of Gene Expression. Chapter 18. Background. Both prokaryotes and eukaryotes alter gene expression in response to their changing environment Efficient bacteria (by chance) produce only the proteins they need. They are selected for by their environment

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Regulation of Gene Expression

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  1. Regulation of Gene Expression Chapter 18

  2. Background • Both prokaryotes and eukaryotes alter gene expression in response to their changing environment • Efficient bacteria (by chance) produce only the proteins they need. • They are selected for by their environment • So the population evolves to produce even more efficient future generations • So how do bacteria regulate enzyme or protein production?

  3. Regulation

  4. Background (2) • Gene regulation or feedback inhibition • Regulation of Gene Expression in prokaryotes is accomplished by the OPERON • OPERON • A cluster of functionally related genes can be under coordinated controlby a single on-off “switch” • The regulatory “switch” is a segment of DNA called an operator usually positioned within the promoter • An operonis the entire stretch of DNA that includes the operator, the promoter, and the genes that they control

  5. Operon Model

  6. Operon • 3 Main Components • Operator – Controls RNA Poly’s access to the genes (DNA) • Found in Promoter region or promoter  genes • Promoter Region – Where RNA Poly attaches • Genes of the Operon – stretch of DNA required for total enzyme or protein production

  7. What regulates the Operator? • Regulatory Genes • Located away from the operon • Produce repressor proteins that may bind to operator • If operator is bound, then RNA Poly is “cock-blocked” • RNA Poly can’t “holla” at the operator

  8. Regulatory Genes

  9. Repressible Operon • Turned ON, but can be turned off • Like neutering a tomcat • Anabolic in nature • Repressor is normally inactive, but can be activated • If Repressor is activated, then it represses (STOP) the operon (TURNED OFF) • Corepressor – protein produced by the operon can feedback inhibit the operon • Corepressor binds & activates repressor protein = TURN S THE OPERON OFF

  10. Inducible Operon • Normally off, but can be turned on • No way I am giving a non-AP Bio example on this one • Typical of catabolic pathways • Repressor protein is always active • Inducer binds and Inactivates the repressor protein • With repressor removed, RNA Poly can now “spit game” (Ewww) at the DNA • Operon is now turned ON

  11. Modeling an Operon • What materials would you need to construct a good model of both a repressible and inducible operon? • Get into groups of 2-3 (no more than 3) and determine 1. What materials would you need? -- List ALL needed materials 2. Develop the directions for building the model of both the repressible and inducible operon. 3. Every group member must be able to explain your proposal

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