BME 80H Lecture Notes - Lecture 21: Y Chromosome, Sexual Differentiation, Gamete
11 Jun 2018
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Lecture 21- 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 the sex of the child/
maleness (due to its SRY /TDF gene)
- The XO system is the x to autosome ratio, rather than hetero or
homo so it is X or XX if they have the XY they are fertile just the
X is infertile
- Roosters and ZZ and ZW
B. In humans, the male gamete determines the sex of the offspring
(figure 7.11).
female = homogametic
- All gametes contain an X chromosome
male = heterogametic
- Half of the gametes have an X and half have a Y
C. Expect equal numbers of male and female offspring = sex ratio
- Not exactly equal
- 1.06 males = 1.00 females at birth
- Evens out as time progresses
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Document Summary
Lecture 21- sex determination and differentiation (ch 7 p. 159-170/158-168: how sex is determined, animals have differing modes of sexual differentiation (figure 7. 10) In humans the y chromosome determines the sex of the child/ maleness (due to its sry /tdf gene) The xo system is the x to autosome ratio, rather than hetero or homo so it is x or xx if they have the xy they are fertile just the. Roosters and zz and zw: in humans, the male gamete determines the sex of the offspring (figure 7. 11). female = homogametic. All gametes contain an x chromosome male = heterogametic. Half of the gametes have an x and half have a y: expect equal numbers of male and female offspring = sex ratio. 1. 06 males = 1. 00 females at birth. Sex differentiation: becoming male or female: early development, normal male and female development (figures 7. 13, 7. 14, handouts)
