The Meaning of Sex: Genes and Gender

Lecture 2 – Hermaphrodites: The Safer Sex

by Barbara J. Meyer, PhD

  1.  1.  Start of Lecture 2
  2.  2.  Introduction by HHMI Vice President Dr. Peter Bruns
  3.  3.  Introductory interview with Dr. Barbara Meyer
  4.  4.  Why do we study model organisms?
  5.  5.  Introduction to the nematode Caenorhabditis elegans
  6.  6.  Anatomy of C. elegans: every cell is known
  7.  7.  C. elegans has two sexes: male and hermaphrodite
  8.  8.  Video: C. elegans mating
  9.  9.  C. elegans sperm
  10. 10.  Video: Amoeboid sperm of C. elegans
  11. 11.  A behavior gene in C. elegans is related to a human gene important in kidney function
  12. 12.  Life cycle of a hermaphrodite
  13. 13.  Fertilization mechanism in C. elegans
  14. 14.  Early embryonic development of C. elegans
  15. 15.  Video: From fertilization to egg laying in C. elegans
  16. 16.  Using mutations to study sex determination in C. elegans
  17. 17.  Activation of sex-determining gene
  18. 18.  Student question: Why can't human hermaphrodites self-ferilize?
  19. 19.  Student question: Why aren't there any female worms?
  20. 20.  Student question: Do hermaphrodites use male sperm preferentially?
  21. 21.  Student question: Do male sperm permanently displace hermaphrodite sperm?
  22. 22.  Student question: Did hermaphrodites evolve from females?
  23. 23.  Student question: Can hermaphrodites mate with each other?
  24. 24.  Student question: At what stage can you determine the sex of the worm?
  25. 25.  The basis for sex determination in C. elegans
  26. 26.  Activity of xol-1 sex-determining gene is dependent on the ratio of X chromosomes to autosomes
  27. 27.  The balance of X signal elements (XSEs) and autosomal proteins regulates xol-1 activity
  28. 28.  Demonstration: Balance of molecules in XO
  29. 29.  Demonstration: Balance of molecules in XX
  30. 30.  Demonstration: Balance of molecules in XX with lower levels of XSEs
  31. 31.  Demonstration: Balance of molecules in XX with much lower levels of XSEs
  32. 32.  Review of the central dogma of genetics
  33. 33.  An X signal element (XSE) represses transcription of xol-1
  34. 34.  An XSE also acts to prevent proper splicing of xol-1 mRNA transcript
  35. 35.  Summary of repression mechanisms of xol-1
  36. 36.  Does xol-1 at low levels have any functions?
  37. 37.  Student question: What is the purpose of the low level of xol-1 in hermaphrodites?
  38. 38.  Student question: Is xol-1 comparable to SRY in mammals?
  39. 39.  Student question: What is the difference between the blue and yellow XSEs in the demo?
  40. 40.  Student question: What do we know about human hermaphrodites?
  41. 41.  Student question: Is it possible to produce a worm that lacks xol-1?
  42. 42.  Student question: Do all organisms require a gene to be switched on for male development?
  43. 43.  Student question: Can you add xol-1 to a hermaphrodite and make it male?
  44. 44.  Closing remarks by HHMI Vice President Dr. Peter Bruns

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