Chromosomes and Hormones involved in Sex & Gender Flashcards
How are chromosomes involved in sex/gender?
- Humans have 23 pairs of chromosomes
- Females have XX and males have XY chromosomes.
- The Y chromosome contains the SRY gene, which causes the male physical development at the fetal stage.
- SRY gene creates (sex-determining region Y protein’ - a transcription factor that binds to DNA to control other genes.
How is the sex developed?
- Every foetus appears the same until a few weeks after conception.
- Sex organ development is complete at around 3 months after conception.
- Lutropin is then produced in both sexes in the adrenal glands.
- Testes contain Leydig cells, which respond to lutropin by producing testosterone.
- Testosterone drives further male development.
What are the 2 intersex atypical sex chromosome patterns?
- Klinefelter’s syndrome (1 in 10,000 males)
- Turner’s syndrome (1 in 2,000 females)
What is Klinefelter’s syndrome?
- XXY configuration (extra X chromosome)
- Child born with penis and develops male traits
- Usually infertile, lack muscular definition and have feminised masculine characteristics
What is Turner’s syndrome?
- Due to ‘X0’ configuration (one chromosome is damaged or missing)
- Born with both vagina and womb but underdeveloped ovaries
- No monthly period, physically short/stout build
- Can have webbed neck, narrow hips, irregular internal organs.
How is testosterone involved in sex/gender?
- Produced before birth
- A foetus can be insensitive to testosterone (intersex)
- No formation of male genitalia
- Often born/raised as girls because no penis/testicles are visible
- Some are identified as XY and raised as boys
- Brain development is affected by testosterone. Studies show XX females are ‘tomboyish’ and prefer masculine activities in this case.
- Testosterone surges in puberty drive secondary male characteristics
How is oestrogen involved in sex/gender?
- Present in all cases for the foetus - default gender is female.
- Oestrogen level is associated with smaller brain size.
- Promotes secondary female sex characteristics in puberty.
- Controls menstrual cycle through increasing blood flow to uterus.
- Elevated during pregnancy.
How is oxytocin involved in sex/gender?
- Produced in pituitary in response to skin-to-skin contact.
- Promotes bonding behaviour.
- Causes milk production.
- Enables post-orgasm bliss.
- Helps in wound-healing.
- Dampens fight-or-flight response in women and is related to ‘tend and befriend’.
Evaluate the use of hormones/chromosomes in explaining sex and gender.
P - Biological determinism –> Money & Erhardt (1972) claimed only sex rearing determined gender.
E - Money advised parents to raise intersex children however they liked, regardless of genetics/hormones . ‘John/Joan’ study (David Reimer) - unsuccessful suggesting gender is biologically determined
E - Further studies support; Reiner & Gearhart (2004).
L - Therefore, gender is due to nature even though nurture may contribute.
P - Real-world applications
E - Intersex people who will develop problems, can be identified at birth and given proper treatment during puberty. This can negate the effects almost entirely.
E - Olympics ruled in 1991 that genetic sex didn’t matter for participation, after testing since 1968. Individuals who are obviously physically male are still excluded from female events.
L - This means biological research into gender development is ecologically valid.