Chapter 5 Sexdetermination and sex-linked characteristicsPartISexdetermination
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
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 VenusBezeichnungder Himmelskorper.Sonne.2Jupiter.Mond.专Saturn.CMerkur.Uranus0Venus.Neptun?.Erde.Astraa.4Mars.2Hebe.Vesta.Iris.?￥Juno.Flora.TPallas.Metis.CCeres
Men are from Mars, Women are from Venus
Chromosomal sex determining system (XY)Sex chromosome vs.AutosomeCRDanSERSCEDREACSEaaDats-BeasttCEX23u)EDXeRTerrEar34ateAEgTEr101112789SEEeEsaelGRAEECEsatc4G.13161415福Ea81A43E50ONS202219
Chromosomal sex determining system (XY) Sex chromosome vs. Autosome
Sexual differentiation is very commonSexualdifferentiation occurs inorganisms aslowas ontheevolutionary scale as bacteria and single-celled eukaryotic algaeChromosomalDNAChromosomalDNAFplasmidDPilusDonor(F+Strain)Recipient (F-)
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 reproductionin Chlamydomonasreinhardtiiplus agglutininsminusagglutininsFusionMeiosisZygoteMatingGGametogenesis
Sexual reproduction in Chlamydomonas reinhardtii 6
Sexual dimorphismSecondarysexualdifferentiationPrimarysexualdifferentiation(gonads)
Sexual dimorphism Secondary sexual differentiation Primary sexual differentiation (gonads)
Unisexual vs. BisexualasselsHermaphrodite（雌雄同体）
Unisexual vs. Bisexual Hermaphrodite (雌雄同体)
1. Different sex determining systemDNuclearstructureoftheGrasshoppersperm
1. Different sex determining system Nuclear structure of the Grasshopper sperm
(a)Eg. 1 Nematodes(b).Caenorhabditiselegans· XX/XO systemHermaphroditeSelf-fertilizationXXX.Ratio of sex chromosomes toMaleHermaphroditeautosomes(99%)Cross-fertilization42X/2A=1XXX.1X/2A=0.5MaleHermaphrodite(50%)(50%)
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