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BGYB30H3 Lecture 22 Notes Reproduction and Development 2-Nov 24

Biological Sciences
Course Code
Ingrid L.Stefanovic

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BGYB30H3 Lecture 22 Notes
-sperm and egg come together to form a zygote with 23 pairs of chromosomes
-autosomal chromosomes develop into human body form
-Y chromosome stimulates development of male
-SRY gene is the sex determining region of the Y chromosome, causing male reproductive
-absence of an X chromosome is fatal
-dµv[Çv}u causes an underdeveloped reproductive system, which leads to
x Short stature
x Heart problems
x Poor breast development
-}oÁ]Zdµv[Çv}u}voÇZÀ}vyZ}u}}u (XO)
-<o]v(o[Çv}uinvolves an extra X chromosome (XXY), causing males to develop
female sex characteristics such as
x Altered upper to lower body ratio
x Female pubic hair pattern
x Sparse body hair
x increased growth rate in childhood
x taller than average height
x learning disabilities
x acne
-XXYY syndrome involves the development of male and female characteristics, causing
x gynecomastia: development of breasts in males
x taller height
x mood swings
x intellectual disabilities
x low muscle tone
x low testosterone
x sterile
-Swyer syndrome/XY gonadal dysgenesis is an absence or mutation of SRY chromosomes
-females have no functional female gonads in Swyer syndrome
-differentiation of the gonads occurs during the 7th week of development in embryos
-bipotential gonads have a pair of Wollfian and Mullerian ducts
-SRY gene directs the medulla of the bipotential gonads to form testes
-testes secrete
x anti-Mullerian hormone to degenerate the Mullerian duct
x testosterone to convert Wollfian duct to develop into the male reproductive system
x DHT to cause the development of external genitalia and prostate gland
-absence of SRY gene causes development of female genitalia
-cortex of bipotential gonad develops into ovaries
-no testosterone means that the Wolffian ducts degenerate
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