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Showing Revision 2 created 10/03/2013 by Cogi-Admin.

  1. I'm Uta Francke. I'm a Human Geneticist originally from Germany as you can hear.
  2. And I'm an Emeritus Professor here at
  3. Stanford and also Senior Medical Director at 23andMe.
  4. >> So, we have three billion based pairs and just one copy
  5. of the human genome. And we, we've learned that, you know we have
  6. two copies of the human genome of the nuclear genome in, in our
  7. cells. And we've been learning a bit about the coding regions, the protein
  8. coding regions. what, what can you tell us about the relative size of
  9. the protein coding regions of the genome versus the sort of non coding regions?
  10. >> The big question was how many protein coding genes
  11. are there in the genome? And initially, before the genome project
  12. the, the number that's been kicked around was like 100,000.
  13. Sort of, a wild guess. And then, between 2000 and 2003,
  14. there was an official betting game going on
  15. where people could put down a dollar and a
  16. number. And then years later, it was $5 and then it was $20 because in a way, it
  17. became more difficult. And everybody could only put on
  18. down one bet. About 150 people put down the
  19. bet, and their range, the ranges of their guesses
  20. went from, you wouldn't believe it. 25,000 to 150,000.
  21. >> Wow.
  22. >> So nobody had really any good idea.
  23. The mean was around 61,000 genes. And when the
  24. first draft was published they said, well we had a brief look at it and we think
  25. it's between 30 and 35,000. And when it
  26. was finally finished, the number had come down to
  27. 20 to 25,000. And many people were surprised because
  28. this is hardly any more than the, the round
  29. worm or the fruit fly. So the humans are so much
  30. more complex, shouldn't they have more protein coding genes? So the
  31. complexity cannot be immediately dedu, deduced from the number of genes,
  32. when you don't know what these, these genes can be used for.
  33. >> So what percentage of the genome
  34. is actually made up of coding region, roughly?
  35. >> It's only 1 to 2%. And so all this other,
  36. you know, 90, 98 to 99% then. I mean, a lot of people who you know, are
  37. just learning about the genome may be wondering,
  38. what exactly is the rest of that sequence doing?
  39. >> You see, originally people thought it was just junk.
  40. It was just a virus getting in and replicating itself.
  41. >> Mm-hm.
  42. >> And, in recent years, people started to look at how much of that
  43. sequence is being made into RNA. How
  44. much is being transcribed. And to everyone's
  45. surprise more than 80% is actually made into a copy of RNA. And these RNAs have
  46. all kinds of interesting functions. For example, to regulate activity of
  47. other genes. To regulate the activity of messenger RNAs, how they are being
  48. translated. And many different function that the
  49. RNAs have. Some of them are structural.
  50. There are RNA set as structural components
  51. of the ribosome. And otherwise, outside of the
  52. coding sequence are control regions that are
  53. important to regulate the activity of each gene.
  54. >> I see. So, we learn in this lesson about messenger RNA.
  55. >> Mm-hm.
  56. >> mRNA. And so what you're saying, there are actually other kinds of
  57. RNAs that can be made besides mRNA that doesn't get turned into protein?
  58. >> That's right.
  59. And what was found out recently, that you remember
  60. there are two strands in the DNA and the messenger
  61. RNAs only made of one strand that gives the
  62. information for the protein. But what is being found out
  63. now is that there are anti-sense RNAs that actually
  64. the other strand of DNA can also be made into
  65. RNA. It goes in the opposite direction. It has
  66. no coding function for proteins, usually not, sometimes it does.
  67. But it has regulatory function. And you just can imagine, if a gene
  68. is transcribed in the other direction, then
  69. the transcription of the messenger RNA has
  70. a problem. You know, it runs into, it's a train wreck, right? So
  71. there was a regulation of gene activity by anti sense RNA that's one mechanism.
  72. >> Right. So it sounds like maybe some of the
  73. complexity of different species or complexity of cells is in part
  74. not so much the, the sheer content. The number of genes you have,
  75. but maybe how you regulate all of those genes together to, to create something.
  76. >> What we are finding out now is that the genomic
  77. regions communicate with each other. Like you can have an enhancer region
  78. that is downstream away from the gene or even in an entrant
  79. of another gene that then falls over, communicates with the promoter and
  80. sets in motion the messenger RNA sentences. So the
  81. whole genome is three-dimensional. It's not just a one
  82. dimensional series of letters. There's a lot of three-dimensional
  83. arrangement and interaction that's very important for its function.