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CHROMOSOMES AND HORMONES IN SEX AND GENDER - Coggle Diagram
CHROMOSOMES AND HORMONES IN SEX AND GENDER
overview
biological sex is determined by genes
each pair of chromosomes carry genes that control different characteristics
biopsychologists assume that gender identity arises from biological processes, as a result of how their brain works
humans have 23 pairs of chromosomes - one pair determines an individuals sex
males and females differ in their sex chromosomes
females have XX, males have XY
development - testosterone
in male embryos, the
SRY gene
on the Y chromosome causes the gonad to develop into testes, which then secrete testosterone, when foetus is around 3 months old
testosterone stimulates the development of the male sex organs, but also cause the male brain to develop differently from the female brain
during prenatal development all individuals start out the same - external genitalia that look feminine
testes/ovaries therefore strongly influence gender development, through the effects of hormones
there is usually a direct link between individuals chromosomal sex, their internal genitalia (ovaries or testes) and external genitalia (vagina or penis)
reiner and gearhart 2004
studied a sample of 14 children born with cloacal exstrophy -birth defect, many abdominal organs are exposed, splitting both male and female genitalia
provided some insight into what can happen when genetically male children are sexually reassigned female and raised as girls
they were reassigned female at birth (born genetically male)
findings: 8/14 identified themselves as boys
all of the participants had at least male typical attitudes and interests
provides some support for the argument that biological variables have an impact on gender identity and behaviour
hormones
eg exposure to high levels of testosterone before birth, may lead to a more masculinised brain and behaviour
testosterone (androgen) affects typically males behaviours such as dominance or aggression
males and females produce different sex hormones in varying quantities which have an effect on behaviour
testosterone stimulates the development of male secondary sex characteristics that emerge at puberty
money and ehrhardt 1972
the girls exhibited male type behaviours eg playing energetic sports, and an absence of female type behaviours eg. playing with dolls
this suggests that testosterone has a strong influence on gender behaviour
reported on a sample of girls whose mothers took drugs containing testosterone during pregnancy
testosterone and brain development
such as areas linked to spatial skills and behaviours like aggression and competitiveness
the sexually dimorphic nucleus SDN is larger in males
testosterone is thought to act on the hypothalamus, without this the brain develops as a female
oestrogen
oestrogen has psychological and behavioural effects, such as premenstrual tension PMT, which is associated with emotionality and irritability
oestrogen feminises the brain, promoting neural interconnections for a more distributed, bilateral brain
promotes the development and maintenance of female characteristics and regulates menstruation
fitch and deneberg
this led to changes in the corpus callosum area and therefore affected connectivity between hemispheres
this supports the idea that oestrogen is involved in the feminisation of the brain
suppressed production of oestrogen by removing ovaries from female rats
oxytocin
oxytocin affects female social behaviour such as mate selection, pair boding, monogamy
the love hormone produced in both males and females - helps facilitate childbirth
strength
for example, in all cultures studied, men are found to be more aggressive than women
this suggests that male traits, such as aggression, are biologically determined through exposure to testosterone
the biological view of gender is supported by cross cultural studies that have found universal features of gender
weakness
research carried out with non human animals there is a need for caution in assuming that the results apply to humans
the physiology of humans and animals, like rats and mice, especially in terms of brain functioning is very different and human development and behaviour are much more subject to social and cultural influences
extrapolation issues
only provides limited support for the idea that hormones influence our behaviour