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Chapter 16 Control of Gene Expression

Chapter 16 Control of Gene Expression. Topics to discuss. DNA binding proteins Prokaryotic gene regulation Eukaryotic gene regulation. 6 groups of DNA-binding regulatory proteins have been identified. Prokaryotic Gene Regulation. Operons Operons provide coordinate expression.

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Chapter 16 Control of Gene Expression

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  1. Chapter 16Control of Gene Expression

  2. Topics to discuss • DNA binding proteins • Prokaryotic gene regulation • Eukaryotic gene regulation

  3. 6 groups of DNA-binding regulatory proteins have been identified

  4. Prokaryotic Gene Regulation

  5. Operons • Operons provide coordinate expression

  6. A model operon

  7. Now let’s look at 2 groups of operons • Negative inducible operons • Negative repressible operons

  8. Negative inducible operon INDUCIBLE

  9. Turned on

  10. repressor

  11. Now let’s look at 2 specific operons • The Lactose operon • The Tryptophan operon

  12. Francois Jacob and Jacques Monod 1961 • Studied lactose metabolism in prokayotes

  13. 1. Disaccharide 2. Monosaccharide Lactose Glucose Sources of prokaryotic energy

  14. Building the lac operon

  15. Lac Operon and Proposed Arrangement with control I gene I P O Z Y A Not technically part of the “operon”

  16. Lactose Metabolism Requires Coordination of all these genes!

  17. Negative inducible operon

  18. Conditions: No glucose but lactose is present

  19. Lactose Metabolism Requires Coordination of all these genes!

  20. Lac Operon and Proposed Arrangement with control I gene I P O Z Y A Not technically part of the “operon”

  21. Overview of: Mutational Analysis of the lac operon3-24p. Lab manua

  22. Monod and JacobDiscovery of lac operon control

  23. Try out your ability to reason through the questions.

  24. No Lactose - 1 + 2 3 4 5 6 7 8 9

  25. Now, back to glucose and the lac operon! Lac

  26. Question: what happens when both lactose and glucose are present together in the same cell?

  27. Conditions: glucose present and lactose

  28. Need to understand this reaction Adenylyl cyclase ATP Cyclic AMP + catabolite activator protein Glucose may inhibit this enzyme

  29. The promoter needs to be in an ideal conformation for RNA polymerase.

  30. How CAP and cAMP affects the promoter

  31. Trypthophan Operon

  32. Trypthophan Operon • 5 genes involved in the synthesis of the amino acid trypthophan

  33. Negative repressible operon

  34. 2 shapes to the mRNA

  35. attenuation

  36. Eukaryotic Gene Regulation

  37. Do eukaryotes show coordinate gene regulation? Yes, the same response element may be found in related genes.

  38. Changes in Chromatin structure and eukaryotic gene regulation • DNase hypersensitivity • Histone acetylation • DNA methylation

  39. For Your Information Next 4 slides

  40. Experimental tests on the repressor: • I+ cells synthesize full levels of the lac enzymes only in the presence of an inducer • I- mutations NO DNA BINDING ACTIVITY, TRANSCRIPTION OCCURS EVEN IN ABSENCE OF INDUCER! • Is mutation NO LACTOSE BINDING ACTIVITY but has DNA BINDING ACTIVITY. NO TRANSCRIPTION EVEN WITH INDUCER! • Oc mutation: constitutive activity

  41. Trans (across) acting product

  42. Oc= constitutive operator, notice how it affects transcription.

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