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Sex determinants

Sex determinants. Dr. Sanjaya Adikari Dept. of Anatomy. Objectives. Explain the role of sex chromosomes in sex determination Highlight the role of Y chromosome in fetal sex determination. Male. Female. chromosomal sex. cell. XX. XY. gonadal sex. Ovaries. Testicles. gonads.

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Sex determinants

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  1. Sex determinants Dr. Sanjaya AdikariDept. of Anatomy

  2. Objectives • Explain the role of sex chromosomes in sex determination • Highlight the role of Y chromosome in fetal sex determination

  3. Male Female chromosomal sex cell XX XY gonadal sex Ovaries Testicles gonads external genitalia Labia majora & minora vulva, vagina Penis, scrotum assigned sex general appearance Facial hair dress Breasts dress

  4. Chromosomal sex • Determined at the time of fertilization • 46, XX female • 46, XY male • What determines the sex? • Presence of two ‘X’ chromosomes? • Presence/absence of ‘Y’ chromosome?

  5. Individuals resulting from non-disjunction of sex chromosomes

  6. XY XX nondisjunction Y XX O X XXX XXY XO OY Super females Klinefelter’s syn Turner’s syn lethal Can one get XYY?

  7. Live with‘X’&Sex with‘Y’

  8. indifferent stage female male External genitalia

  9. Role played by hormones XY XX ovaries testicles androgens oestrogen male external genitalia female external genitalia male secondary sex characteristics female secondary sex characteristics

  10. Determining the number of X and Y Sex chromatin Barr body for X F body for Y

  11. Barr body Barr body • Condensed inactive ‘X’ in interphase nuclei • Near the nuclear membrane • All ‘X’ in addition to one ‘X’ become BB’s

  12. F body F body • Fluorescence stained ‘Y’ • This ‘Y’ is active

  13. ?? XX XXY XO XYY One BB No FB One BB One FB No BB No FB No BB Two FB

  14. References • http://www.people.virginia.edu/~rjh9u/sexdet.html • http://www.dushkin.com/connectext/psy/ch10/biodet.mhtml • http://www.aaa.dk/TURNER/ENGELSK/XYY.HTM#name • Review of medical physiology by William F. Ganong • Medical embryology by Jan Langman

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