Chromosomes and Hormones involved in Sex & Gender

Question 1

How are chromosomes involved in sex/gender?

Answer 1

• 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.

Question 2

How is the sex developed?

Answer 2

• 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.

Question 3

What are the 2 intersex atypical sex chromosome patterns?

Answer 3

• Klinefelter’s syndrome (1 in 10,000 males)

- Turner’s syndrome (1 in 2,000 females)

Question 4

What is Klinefelter’s syndrome?

Answer 4

• XXY configuration (extra X chromosome)
• Child born with penis and develops male traits
• Usually infertile, lack muscular definition and have feminised masculine characteristics

Question 5

What is Turner’s syndrome?

Answer 5

• 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.

Question 6

How is testosterone involved in sex/gender?

Answer 6

• 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

Question 7

How is oestrogen involved in sex/gender?

Answer 7

• 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.

Question 8

How is oxytocin involved in sex/gender?

Answer 8

• 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’.

Question 9

Evaluate the use of hormones/chromosomes in explaining sex and gender.

Answer 9

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.