1. Control of Gene Expression
More about bacteria!

2. Now part of the rest of the bacteria chromosome can be transferred to another bacteria cell:
Recombination exchanges segments of DNA.

3. Why would a bacteria want to control gene expression anyway?
In order to adjust to the changing environment.
For example: Amino acid, Tryptophan (found in chicken, turkey, fish, soybeans, etc.)
E. coli can make their own tryptophan, but are they going to bother making their own when Thanksgiving rolls around?!
But first…some VOCABULARY!

4. The entire stretch of DNA required for enzyme production.
Operon
The entire stretch of DNA required for enzyme production.
Includes the operator, promoter and genes they control.

5. Promoter
Region where RNA polyermase binds

6. Operator Acts as an “on-off switch”
Region between the promoter and the first gene

7. Repressor
Protein that binds to the operator and blocks the attachment of RNA polymerase

8. Corepressor
A small molecule that cooperates with a repressor protein to switch an operator off

9. Regulatory Gene
The gene that produces repressors

10. Inducer
A molecule that inactivates the repressor

11. Now let’s put it all together!

12. How do all the parts interact?
NO tryptophan in environment:
Repressor does not bind to the operator
RNA polymerase attaches
Enzymes are made that make tryptophan

13. What happens if we just ate some turkey?!
Tryptophan in the environment:
Tryptophan acts as a corepressor and binds to the repressor.
The repressor now has the correct shape to bind to the operator.
RNA polymerase can NOT attach to the promotor
Tryptophan synthesis is STOPPED!

15. Repressible vs. Inducible Operons
Repressible operon: one that is inhibited when a specific small molecule binds to a regulatory protein
Normally ON: active
Function in anabolic pathways (making)
Inducible operon: one that is stimulated when a specific small molecule interacts with a regulatory protein.
Normally OFF: inactive
Function in catabolic pathways (breaking down)

16. Inducible operon example…
The lac operon contains genes that code for enzymes that break down lactose.
Your mom forgot to buy milk: your bacteria are not going to make any enzymes for the breakdown of lactose (OFF)

17. No milk = operator OFF

18. Got milk = operator ON

19. Do you know your vocabulary?!
Let’s find out!

20. Clue #1 The entire stretch of DNA required for enzyme production.
Includes the operator, promoter and genes they control.

21. Operon

22. Clue #2
Region where RNA polyermase binds

23. Promoter

24. Clue #3 Acts as an “on-off switch”
Region between the promoter and the first gene

25. Operator

26. Clue #4
Protein that binds to the operator and blocks the attachment of RNA polymerase

27. Repressor

28. Clue #5
A small molecule that cooperates with a repressor protein to switch an operator off

29. Corepressor

30. Clue #6
The gene that produces repressors

31. Regulatory Gene

32. Clue #7
A molecule that inactivates the repressor

33. Inducer