Showing Revision 1 created 09/29/2013 by Cogi-Admin.

1. Title:
2. Description:

3. 280 0:00 - 0:05
   Okay, this is a really tricky problem. But the answer is the last one right
4. 4787 0:05 - 0:14
   here. Methianine or M, P or Proline, D or Aspartate, or S or Syrine. Now if
5. 14160 0:14 - 0:16
   you had trouple getting this, let's walk through
6. 16440 0:16 - 0:20
   it really quick. I can immediately get rid
7. 20000 0:20 - 0:22
   of these first three answers over here for
8. 22080 0:22 - 0:26
   one very important reason. We have one start
9. 25530 0:26 - 0:31
   codon and it's Methanine. A ribosome is looking for that start codon
10. 31240 0:31 - 0:38
    and if I read my mRNA ACA, no that's not it, CAG, no that's not it, AGA, no
11. 37660 0:38 - 0:45
    that's not it, GAU, no that's not it, AUG, there it is, AUG. AUG's my
12. 44730 0:45 - 0:48
    star codon. Right? That means I get a
13. 47510 0:48 - 0:51
    Methionine. None of these start with Methionine. All
14. 51360 0:51 - 0:55
    of these start with Threonine which is an
15. 54750 0:55 - 0:57
    ACA. So, if you just start at the beginning,
16. 57240 0:57 - 0:59
    you would have started with the Threonine and probably
17. 59050 0:59 - 1:02
    gotten one of these three answers. This is the
18. 62170 1:02 - 1:08
    one, I think if you end up going all the way to the very end, and the second
19. 67500 1:08 - 1:10
    one, is if you might have noticed a stop
20. 70230 1:10 - 1:16
    codon. ACAGAUGCCUGA stop, right? And some of you might
21. 76410 1:16 - 1:19
    have stopped completely and just put TDA, or if you
22. 79090 1:19 - 1:22
    stopped and then kept going, right, that would not have
23. 82250 1:22 - 1:26
    been accurate, as we see over here. Is a better
24. 85585 1:26 - 1:28
    example of why you wouldn't want to do that. We know
25. 87960 1:28 - 1:31
    now that we want to start at AUG, okay, so now
26. 90930 1:31 - 1:33
    we know the first one is Methionine, and because we
27. 92960 1:33 - 1:37
    have a non-overlapping code, our next one is CCU. We
28. 97230 1:37 - 1:41
    don't do UGC or GCC, the next codon is CCU.
29. 101410 1:41 - 1:48
    Go over here. CCU is Proline, so we have a P. They all have a P. The next
30. 107570 1:48 - 1:53
    one is GAU. GAU. Aspartate D, they all have
31. 113420 1:53 - 2:02
    that. The next one would be UCA, UCA Syrine right here.
32. 121920 2:02 - 2:07
    So the next one should be Syrine. They all have that. And then we get to UGA.
33. 126540 2:07 - 2:08
    And you'll notice that UGA is one of
34. 128050 2:08 - 2:12
    our special stop codons. This would tell the ribosome
35. 131600 2:12 - 2:15
    to stop translating right here. And actually the
36. 135420 2:15 - 2:18
    only one that stops is MPDS, this last one
37. 138480 2:18 - 2:21
    right here. The other ones actually keep going.
38. 141050 2:21 - 2:26
    ACC, ACC. Is Threanine, right? They actually thought that
39. 146230 2:26 - 2:30
    they should drop in another amino acid and keep
40. 149550 2:30 - 2:32
    on going. When you get to a stop codon,
41. 151950 2:32 - 2:37
    you stop translating. From AUG to UGA, this would
42. 157200 2:37 - 2:42
    be our actual code that gets turned into protein.