1. Chapter 16 Control of Gene Expression

2. Topics to discuss DNA binding proteins Prokaryotic gene regulation
negative inducible: lac operon
negative repressible: trp operon
Eukaryotic gene regulation

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

5. Prokaryotic Gene Regulation

6. Operons
Operons provide coordinate expression

7. A model operon

8. Now let’s look at 2 (of four) groups of operons
Negative inducible operons
Negative repressible operons

9. Negative inducible operon

10. Turned on

11. repressor

12. Now let’s look at 2 specific operons
The Lactose operon: negative inducible
The Tryptophan operon: negative repressible

13. Francois Jacob and Jacques Monod 1961
Studied lactose metabolism/operon in prokayotes
J. Monod
Won the Nobel Prize in 1965

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

15. Sources of prokaryotic energy
Monosaccharide
Disaccharide
Glucose
Lactose

16. Building the lac operon

17. Lac Operon and Proposed Arrangement with control I geneZ Y A
Not technically part of the “operon”

18. Lactose Metabolism Requires Coordination of all these genes!

19. Negative inducible operon

21. (assume only lactose is present)

22. Next: let’s review just the pattern of expression when:
When only lactose is present.
When only glucose is present.
Glucose and lactose are present in the cell

23. Conditions: Only lactose is present

24. Conditions: Only glucose

25. Glucose and Lactose

26. Summary

27. “Why does the presence of glucose influence lactose metabolism?

28. To answer this question you need to understand this reaction
Adenylyl cyclase
ATP
Cyclic AMP +
catabolite activator protein
Glucose may inhibit this enzyme

29. Now put the pieces all together.

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. Ribosome does not stall

36. Ribosome stalls

37. Changes in Chromatin structure and eukaryotic gene regulation
Histone acetylation
DNA methylation
RNA silencing

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

41. Also remember gene expression through RNA interference!