Chromosomes, hormones & atypical chromosome patterns

• what does biology believe is the cause of gender differences

  assume that gender and sex are related and that biological differences (chemistry/hormones) between sexes are the cause of gender differences
• what are chromosomes

  - chromosomes are in every cell of the body and they contain genes

  
• what are genes


  genes are sections of DNA that determine a person's characteristics

  
• how many chromosomes are in the body

  46 chromosomes, 23 pairs
• what contains the x and y chromosomes

  egg = X chromosomes

  sperm = Y chromosome

  
• what does the Y chromosome carry

  SRY - sex determining region
• what does the SRY produce - what does this develop into

  androgens (male sex hormone) such as dihydrotestosterone, so the foetus develops into a boy, without androgens the foetus develops into a female
• outline male gender development according to the biological approach

  XY --> androgens --> development of testes --> testosterone

  --> development of male sex organs & masculinises the brain
• outline female gender development according to the biological approach

  XX --> development of ovaries --> produces oestrogen

  --> development of female sex organs and feminises the brain
• what influences gender development

  hormones influence gender development

  chromosomes initially determine a person's sex
• what happens if a baby has an insensitivity to hormones

  genetic males would develop as a female
• what is the role of hormones in the womb and at puberty

  prenatally in the womb: hormones act on brain development and cause reproducitve organs to develop

  at puberty: a burst of hormones trigger the development of secondary sexual characteristics (males & females produce many of the same hormones but in different amounts)
• give 3 examples of hormones

  - testosterone

  - oestrogen

  - oxytocin
• what gland is testosterone and oestrogen produced from

  gonads
• what are the physical effects of testosterone on the body

  masculinises the brain
• what is the impact of testosterone on behaviour/emotions

  increased aggression and competitiveness
• what is a however argument for effects of testosterone

  Eisenegger: observed women playing a bargaining game, those who believed they had been given a dose of testosterone behaved in an unfair way, than those who believed they had a placebo

  This demonstrates the effects of expectations on behaviour changes and would mean there isn't a simple relationship between hormones and behaviour
• what are the physical effects of oestrogen on the body

  feminises the brain and female reproduction
• what is the impact of oestrogen on behaviour/emotions

  irritability and emotionality, implicated in PMS (pre-menstrual syndrome)
• what gland is oxytocin produced from

  pituitary gland
• what are the physical effects of oxytocin on the body


  promotes feelins of bonding (love hormone)

  stimulates birth, labour & lactation in pregnant women
• what is the impact of oxytocin on behaviour/emotions


  more in women than in men. high after giving birth, reduces cortisol to help with bonding
• what is the evidence that supports a link between testosterone and aggression

  Dabbs found that in a prison population that offenders with the highest levels of testosterone were more likely to have committed violent/sexually motivated crimes
• what does this support - however

  supports the influence of hormones on gender identity, as the more aggressive they were, the more testosterone they had

  However, correlational as it's only a link so cannot establish a cause and effect relationship
• what evidence supports a link between hormones and gender differences - suggests

  Van Goozen found that transgender women (male to female) showed decreased aggression and visuo-spatial skills, whilst transgender men showed the opposite

  this suggests that sex hormones do exert some influence on gender related behaviours
• what is a however point to this link

  there's a methodological issue with this study, as it involves a small sample of unusual people, so difficult to extrapolate
• explain the study that found contradictory evidence - outline & findings

  there is contradictory evidence for the role of hormones on behaviour:

  study on 43 males, they were given either a placebo or testosterone injections and no significant differences in agression were found after 10 weeks between the 2 groups
• what does this contradictory evidence suggest - however

  this suggests that hormones may not have a significant effect on behaviour

  However, the expectation of thinking they have more testosterone could cause both groups to become more aggressive
• what is another criticism of the biological explanation of gender

  it's reductionist and focuses too much on nature over nurture
• why is this an issue

  it's seen as too simplistic

  also there is as much variation within genders as between them
• outline the David Reimer case study

  - twin boys, taken for a circumcision

  - 1 boy = penis burnt off, other = no operation

  - boy without penis = rasied as a girl until puberty;

  born Bruce --> raised Brenda --> David

  - psychological effects = commited suicide later in life

  - brother = drug overdoe
• what does this case study show for the biological effects of gender

  + supports that nature overrides gender identity, so suggests that biology determines identity instead of environmental influences
• what is a however for David Reimer's case study

  However, it's a case study so a unique situation and hasn't been replicated, so low reliability and difficult to extrapolate
• However, can it be generalised - other study


  a study on 14 genetic males between 5-16 years old were raised as girls due to a medical condition
• what happened to these genetic males - what does this support

  only 5 continued to live as females

  8 = males by the end of the study

  + supports a biological influence on gender identity and shows possible generalisability for the David Reimer case
• what other study could also support the biological explanation

  the Batista Boys
• what are the 2 syndromes associated with gender

  - Klinefelter's syndrome

  - Turner's syndrome
• what is Klienfelter's syndrome

  people with this are biologically and anatomically male, but they have an extra X chromosome

  ssex chromosome = XXY

  
• how many does it affect

  between 1 in 500 and 1 in 1000 males

  2/3rds of people with it arrn't aware they have it
• what are some physical characteristics of someone with Klinefelter's

  + breast development

  + underdeveloped genitals

  + reduced body hair

  + softening of body contours

  + long limbs