安徽师范大学：《遗传学》课程教学课件（讲稿）Chapter 5 Sex determination

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