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Psychology 2035A/B Lecture Notes - Pubic Hair, Sexual Differentiation, Y Chromosome

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Doug Hazlewood

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Sex & Gender
Part 1: Reproductive Biology
Prenatal Sexual Differentiation
The Genetic Factor
- Begins at conception (sperm fertilizes egg)
- Mothers Egg (“X” sex chromosome)
- Fathers Sperm (“X” or “Y”)
- Genetic female (XX)
- Genetic male (XY)
The Gonadal Factor: (development of reproductive organs: testes or ovaries)
- Depends on Y chromosome
- If Y is present it 1) stimulates development of testes 2) inhibits the
development of ovaries
“True Hermaphrodites” genetic female (XX); with tiny piece of Y chromosome
attached (XXy) y is big enough to stimulate development of testes but not big
enough to inhibit the development of ovaries (has BOTH)
The Hormonal Factor (development of sex organs)
- Testes produce androgens (hormone) when androgens are present a
penis develops (the Adam principle)
- When absent, clitoris and vagina develop (the Eve principle)
The Adrenogenital Syndrome genetic female with unusually active adrenal
gland (produce androgens) develops sex organs that appear to be “male”
clitoris is enlarged, vagina is fused (may look like testes)
The Androgen Insensitivity Syndrome genetic male with normal testes, but
the body is insensitive to androgens (like androgens are not present); sex organs
have “female” appearance (looks like a vagina but has no depth; penis looks like
clitoris and testes remain up inside the body)
If everything is normal after these stages your prenatal sexual differentiation is
complete but you cant reproduce for the next decade
The Puberty Factor (Involves Hormones)
- Girls (10-12), Boys (12-14) age ranges have been decreasing over the past
- Development of Secondary Sex Characteristics
Boys and girls pubic hair and growth spurt
Girls breast development
Boys facial hair, deeper voice, larger penis
- Gonads (reproductive organs) mature:
Menstruation in girls (mature eggs released)
First ejaculation in boys (production of mature sperm)
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