BME 80H Lecture Notes - Lecture 9: Paramesonephric Duct, Epigenetics, Genomic Imprinting
4 Jun 2018
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Lecture #9- Sex Determination and Differentiation (ch 7 p. 159-170/158-168)
I. How Sex is Determined
A. Animals have differing modes of sexual differentiation (figure 7.10)
- In Humans, the Y chromosome determines maleness (due to its
SRY/TDF gene)
B. In humans, the male gamete determines the sex of the offspring
(figure 7.11).
female = homogametic
All gametes contains X chromosome
male = heterogametic
Half of the gametes have an X, other half have a Y
C. Expect equal numbers of male and female offspring = sex ratio
- Not exactly equal
- 1.06 males : 1.00 females ratio @ birth
- Evens out with time
II. Sex Differentiation: becoming male or female
A. Normal Male and Female Development (figures 7.13, 7.14, handouts)
1. Early Development
Gonads:
- Y chromosome present —> testes
- No Y-Chromosome —> ovaries
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Ducts-
- male reproductive ducts (internal)
- Form from the wolffian
- Produce vas deferens, seminiforous tubules, other internal
reproductive structures
- Female reproductive ducts
- Mullerian
- Produce fallopian tubes
-
2. Phenotypic Sex Development (genitalia development) involves a
different pathway and different genes than gonad (testes and
ovaries) and duct development.
- These genes are located on autosomes
- Likely located on X-chromosome as well
Testosterone —> DHT —> genitalia development
B. When the Phenotypic Sex doesn't match the Genotypic Sex = Intersex.
(figure 7.13c, handouts)
1. Androgen insensitivity (XY female)
Androgen = male sex hormones
Testosterone & DHT
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Lecture #9- sex determination and differentiation (ch 7 p. 159-170/158-168: how sex is determined, animals have differing modes of sexual differentiation ( gure 7. 10) In humans, the y chromosome determines maleness (due to its. Sry/tdf gene: in humans, the male gamete determines the sex of the offspring ( gure 7. 11). female = homogametic. All gametes contains x chromosome male = heterogametic. Half of the gametes have an x, other half have a y: expect equal numbers of male and female offspring = sex ratio. 1. 06 males : 1. 00 females ratio @ birth. Sex differentiation: becoming male or female: normal male and female development ( gures 7. 13, 7. 14, handouts, early development. Produce vas deferens, seminiforous tubules, other internal reproductive structures. Produce fallopian tubes: phenotypic sex development (genitalia development) involves a different pathway and different genes than gonad (testes and ovaries) and duct development.
