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Florida International University 16

Biology

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14. What occurs in this ar=ea?

15. What is upstream from the transcriptional start site?
16. Each operon has a sequence within or near the promoter to which proteins (activators or repressors) can do what?
17. The operator sequence is found where and does what?
18. When tryptophan is present in the cell, what occurs?
19. What does this achieve?
20. When tryptophan is not present in the cell, what occurs?
21. How is the trp operon negatively regulated?
22. What is a positive regulator?
23. What occurs in E. coli bacteria when glucose is scarce?
24. What is the role of cAMP?
25. What does cAMP bond to?
26. What is CAP?
27. What occurs when cAMP binds to CAP?
28. Where is the CAP binding site located?
29. How does this affect the binding of the RNA polymerase?
30. What occurs when glucose levels fall?
31. What happens when cAMP levels increase?
32. What are inducible operons?
33. What is the role of the lac operon?
34. Where does CAP bind to?
35. What are the two conditions that must be met for the lac opeon to be activated?
36. In E. coli, the trp operon is on by default, while the lac operon is off. Why do you think this is the case?
37. If glucose is absent, what occurs? If lactose is absent, what occurs?
38. If either of these requirements is met, then transcription remains how?