Learning objectives
- What is known about sex and the brain?
- Neural machinery that makes reproduction possible
- How different are the brains of the two sexes
- Is by genetics, brain or behaviour
- Anatomy & physiology of the nervous system
- Activations and organisational effects of st...
Lecture 6 – Riedstra 3,4
Chapter 17
Sex refers to a set of biological attributes in humans and animals.
Gender refers to the socially constructed roles, behaviours, expressions and identities of girls,
women, boys, men, and gender diverse people.
The genetics of sex
- In mammals X & Y
- Males are the heterogametic sex
- Females development is the default state
- Humans have:
o 22 pairs of autosomes
o 1 pair of sex chromosomes
o X has more genes than Y
o X linked diseases:
Colour blindness
Haemophilia
Duchenne muscular dystrophy
- Other combinations:
o X0 —> female (Turner syndrome)
o XX —> female
o XXX —> female
o XY —> male
o XXY —> male (klinefelter syndrome)
o XYY —> male
Prenatal T normal
Increased growth velocity and final height
Normal aggression
Somewhat lower IQ and increased learning difficulties
o XXYY —> male
Sexual differentiation
SRY (Sex determining region on the Y chromosome)
gene encodes for TDF (testis determining factor).
This causes the testis to produce testosterone →
induces development of the Wolffian duct which
develops in to the epididymis, vas deferens and
seminal vesicles —> male.
Mullerian inhibiting factor (activated in the Sertoli
cells) prevents development of the Mullerian duct
(from which uterine tubes, uterus, cervix and part of
the vagina develops.
, The anogenitial distance is the distance between the anus and genitalia and this is larger in males
then in females.
Exception of XX and XY in mammals: the African Pygmy mouse
Different “states” of sex —>
Synthesis of estradiol
Estrogen turns males into demasculinized males, and blocking estrogen (by inactivating aromatase)
synthesis turns females into non-demasculinized females:
Other sex determining systems
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