Sexual Differentiation, Phenotypic Sex - Fundamentals of Physiology | BMS 360, Study notes of Biology

Download Sexual Differentiation, Phenotypic Sex - Fundamentals of Physiology | BMS 360 and more Study notes Biology in PDF only on Docsity! 9 April Sexual Differentiation – Secondary Sex Determination Alfred Jost: Summary Exp 1: remove gonads XX and XY → Mullerian ducts Exp 2: remove gonads + testosterone XX and XY → Wolffian + Mullerian ducts Exp 3: remove gonads of XX + testis fragment XX → Wolffian ducts Phenotypic sex Require testosterone + AMH to form Wolffian ducts and degenerate Mullerian duct AMH = anti Mullerian hormone Development of External Genitalia Starts the same Urethral fold – urethral groove within fold Fold fuses → groove disappears in male Remains separate in female Genital tubercle forms penis or clitoris Development of Male External Genitalia Testosterone + 5α-reductase → dihydrotestosterone (DHT)reductase → dihydrotestosterone (DHT) More potent Disorders of Sex Development Chromosomal nondisjunction One gamete receives both sex chromosomes One gamete receives no sex chromosomes If the error is in meiosis I, all gametes have problems If the error occurs in meiosis II, half of gametes are normal Klinefelter’s syndrome (47, XXY) The extra X chromosome can come from either ovum or sperm Turner’s syndrome (45, XO) YO is lethal Klinefelter’s Variable 1 in 500 Generally infertile Hypogonadism Turner Relatively rare 50% embryos with this genotype die Small stature Webbed neck Infertile XX infant – extra testosterone can masculinize external genitalia Complete androgen insensitivity syndrome Cannot respond to testosterone