Trp operon Animation — Transcript

Full transcript

1. 0:00the true popper on in e.coli contains
2. 0:02five structural genes corresponding to
3. 0:05enzymes that convert Cora's made into
4. 0:07tryptophan the trippy gene contains a
5. 0:11five prime untranslated region or utr
6. 0:14that plays an important role in the
7. 0:16regulatory mechanism called attenuation
8. 0:19the five prime UTR contains four regions
9. 0:23region one encodes a short peptide
10. 0:26containing tryptophan amino acids when
11. 0:30tryptophan levels are high region three
12. 0:32pairs with region for this structure
13. 0:35terminates or attenuates transcription
14. 0:38when tryptophan levels are low region
15. 0:41two pairs with region three this
16. 0:43structure does not terminate
17. 0:45transcription let's examine how these
18. 0:48alternate structures arise RNA
19. 0:51polymerase begins transcribing the DNA
20. 0:54closely following RNA polymerase a
21. 0:56ribosome begins to translate region one
22. 1:00when tryptophan is abundant the ribosome
23. 1:03doesn't slow down at the tryptophan
24. 1:05codons
25. 1:06by the time Region three is transcribed
26. 1:09the ribosome has already moved past the
27. 1:12tryptophan codons to partly cover region
28. 1:14two because region three is prevented
29. 1:17from pairing with region two it pairs
30. 1:19with region four instead to produce the
31. 1:22attenuator which terminates
32. 1:24transcription the structural genes are
33. 1:27not transcribed and therefore no
34. 1:29additional tryptophan is synthesized
35. 1:39when tryptophan is scarce the ribosome
36. 1:43stalls at the tryptophan codons
37. 1:45therefore region 2 is not covered when
38. 1:48region 3 is transcribed allowing regions
39. 1:512 and 3 to form a hairpin that does not
40. 1:53terminate transcription because region 3
41. 1:57is paired with region - it cannot pair
42. 1:59with region 4 and form an attenuator
43. 2:02transcription continues RNA polymerase
44. 2:05transcribes the structural genes which
45. 2:08are translated into enzymes which in
46. 2:10turn synthesize more tryptophan you can
47. 2:14mimic the effect of tryptophan levels by
48. 2:16determining how long the ribosome pauses
49. 2:19at the trip codons