Part I Sex determination Chapter 5 Sex determination and sex-linked characteristics
Outline • Different sex determining system on chromosome • Sex determination in human • Sex determination in drosophila • Sex determination by environment • Sex-linked traits
Men are from Mars, Women are from Venus
Chromosomal sex determining system (XY) Sex chromosome vs. Autosome
Sexual differentiation is very common Sexual differentiation occurs in organisms as low as on the evolutionary scale as bacteria and single-celled eukaryotic algae
Sexual reproduction in Chlamydomonas reinhardtii 6
Sexual dimorphism Secondary sexual differentiation Primary sexual differentiation (gonads)
Unisexual vs. Bisexual Hermaphrodite (雌雄同体)
1. Different sex determining system Nuclear structure of the Grasshopper sperm
Eg. 1 Nematodes • Caenorhabditis elegans • XX/XO system • Ratio of sex chromosomes to autosomes • ♀ 2X/2A=1 • ♂ 1X/2A=0.5 XX X XX X