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Understanding Sex Determination in Mammals: Implications in Livestock Farming

Delve into the sequential process of chromosomal, gonadal, and phenotypic sex determination in mammals, particularly in cattle, poultry, fish, and wildlife. Explore the role of SRY and TDF genes in gonadal differentiation, and the bipotential nature of embryos until the 6th week. Uncover the significance of steroidogenesis in the development of external and internal genitalia. Discover the unique case of freemartin calves and the factors influencing their chromosomal sex.

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Understanding Sex Determination in Mammals: Implications in Livestock Farming

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  1. Sex Determination in Mammals

  2. Importance? • Does it has any economic role in livestock farming system? • Cattle • Poultry • Fish • Wildlife (may be)

  3. A Sequential Process • Chromosomal Sex • Gonadal Sex • Phenotypic Sex

  4. Chromosomal Sex at Fertilization • Female ovum always carries - X X • Male sperm has either – X X or X Y • Y is the smallest human chromosome • Genes are involved in Gonadal differentiation SRY; Sex-determining region Y TDF; Testis determining Factor

  5. Gonadal Sex at 4th Week of Gestation • Mesoderm of urogenital ridge ---- most of the Gonadal cells • Ectodermal cells ------- primordial germ cells (gonocytes) • At 5th week Gonad has • Germ cells • Supporting cells • Stromal or interstitial Cells

  6. Embryo is Bipotential • Until 6th week could develop in male or female phenotype • Default development is female • Embryonic castration develop female • Female urogenital develop in the absence of gonads • Sertoli cells secretes • Mullerian Inhibiting hormone or Anti-Mul.Hormone • Testosterone triggers the development of external and internal genitalia

  7. Comparable Development of Genital Systems

  8. Steroidogenesis • Cholesterol • Pregnelone • Androsteneediol • Testosterone • Estradiol

  9. What is the chromosomal sex of freemartin calves? • Which factor make(s) makes a calf freemartin • Why there is the location of testis and ovary, while they have same embryonic origin?

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