The Meaning of Sex: Genes and Gender

Lecture 3 – Sex and Death: Too Much of a Good Thing

by Barbara J. Meyer, PhD

  1.  1.  Start of Lecture 3
  2.  2.  Introduction by HHMI President Dr. Thomas Cech
  3.  3.  Introductory interview with Dr. Barbara Meyer
  4.  4.  Too many chromosomes: Down Syndrome
  5.  5.  How humans deal with having too many X chromosomes
  6.  6.  How the nematode deals with having too many X chromosomes
  7.  7.  Dumpy (DPY) gene, a dosage-compensation mutant
  8.  8.  The sdc gene affects both dosage compensation and sex determination
  9.  9.  Demonstration: Branched pathway for dosage compensation and sex determination
  10. 10.  Demonstration: The sdc gene is turned on in normal hermaphrodite development
  11. 11.  Demonstration: An sdc-mutant hermaphrodite develops as a male without dosage compensation
  12. 12.  Demonstration: Block sex-determination branch only
  13. 13.  Demonstration: Block dosage-compensation branch only
  14. 14.  How does SDC protein interact with the X chromosome
  15. 15.  How does the male X chromosome avoid dosage compensation?
  16. 16.  What happens in an xol-1 mutant?
  17. 17.  How can you keep an xol-1 mutant from dying?
  18. 18.  How can you manipulate xol-1 mutants to become male?
  19. 19.  Student question: How do you get a 50% reduction in gene activity?
  20. 20.  Student question: Does dosage compensation occur on autosomes?
  21. 21.  Student question: Can a nematode get Down syndrome?
  22. 22.  Student question: How can Turner syndrome have effects if X inactivation occurs?
  23. 23.  Student question: What happens in XXX nematodes?
  24. 24.  Student question: What actually kills when there is no dosage compensation?
  25. 25.  Student question: How do genes in X chromosomes escape inactivation?
  26. 26.  Student question: Do autosomes have genes that determine sex?
  27. 27.  Topics to be covered in the second half of the lecture
  28. 28.  Review of mitotic chromosome segregation
  29. 29.  Dosage-compensation proteins evolved from mitotic proteins
  30. 30.  MIX-1 protein has roles in both mitosis and dosage compensation
  31. 31.  How does MIX-1 carry out these two roles and not get confused?
  32. 32.  Where and when is SMC-4 protein found?
  33. 33.  SMC-4 is only expressed in mitotic cells
  34. 34.  Video: Embryonic cell division in wild type and SMC-4 mutant
  35. 35.  Animation: SMC-4/MIX-1 protein in mitosis
  36. 36.  Animation: SDC/MIX-1 and SMC-4/MIX-1 proteins in dosage compensation and mitosis
  37. 37.  DPY-28 protein is involved in meiosis
  38. 38.  Summary of Lecture Three
  39. 39.  Student question: Can you tag SMC-4 and use it as a marker for mitosis?
  40. 40.  Student question: At what developmental stage does dosage compensation start?
  41. 41.  Student question: Is the dosage-compensation mechanism similar to cell division in any way?
  42. 42.  Student question: How does DPY-28 control the number of crossing-overs?
  43. 43.  Student question: Without SMC-4, would the chromosome stay tangled?
  44. 44.  Closing remarks by HHMI President Dr. Thomas Cech

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