sex chromosomes

• In chlamydomonas

  • In unfavorable nutrient conditions, certain daughter cells can function as gametes
  • The 2 gametes that fuse together during mating aren’t morphologically distinguishable
  • Called isogametes
• C. elegans

  • Males (testes) and hermaphrodites (testa and ovaries)
  • Self fertilization occurs in the hermaphrodites and produces hermaphrodite offspring with <1% male
  • Adult males can mate with hermaphrodites, producing equal proportions of male and hermaphrodite offspring
  • Ratio of X chromosomes and autosomes determine the gender
  • XO - male, XX - hermaphrodite
  • No Y chromosome
• Protenor

  • XX/XO
  • Depends on random distribution of the X chromosome into half the male gametes
  • Presence of XX in a zygotes means female offspring
  • XO - male
• Lygaeus

  • XX/XY
  • XX - female, XY - male