The role of chromosomes and hormones

• Outline the genetic explanation for gender

  Chromosomes are found in all cells and are made of tightly wound dna molecules. Each cell contains 23 pairs of chromosomes, and the 23rd pair are called the sex chromosomes and determine our biological sex.

  
  

  Biological females have XX sex chromosomes and biological males have XY sex chromosomes.

  
  

  A gene on the Y chromosome called the SRY gene causes sex glands to develop into testes which is why this is the genitalia for biological men.

  
  

  Biological women do not have the SRY gene therefore their sex chromosomes develop into ovaries.
• Outline the hormonal explanation for gender

  testes produce testosterone.

  
  

  ovaries produce oestrogen.

  
  

  Both testosterone and oestrogen are produced in smaller amounts from the adrenal glands so both biological sexes produce both hormones, it is just the amount of which they produce that different.

  
  

  These hormones control puberty.

  
  

  Testosterone in biological males causes them to grow facial hair, have deeper voices, and grow taller.

  
  

  Oestrogen in biological females causes them to grow breasts, have periods, and grow taller.
• What is oxytocin's role in gender

  Oxytocin is released from the pituitary gland and females produce much more than men.

  Oxytocin helps females give birth and stimulates lactation.

  
  

  It may also affect behaviour as some studies have linked the hormone with caring behaviour and empathy towards humanity as a whole. Suggesting that the reason women are more empathetic and sensitive is due to the higher levels of oxytocin produced.
• What is testosterones effect on gender

  Studies have shown that people with high levels of testosterone show more signs of aggressive and competitive behaviour suggesting that the reason men are more aggressive is due to the higher levels of testosterone produced.

  
  

  Testosterone also affects the size of our sexually dimorphism nucleus - a cluster of cells in our hypothalamus meaning the SDN is larger in males.

  
  

  Testosterone may also increase brain lateralisation, as studies have shown positive correlations between the two.

  
  

  These may be the causations behind why males and females act differently.
• What is the support for testosterones role in gender

  Research studies from pregnant women who took testosterone showed that girls exposed to high levels of testosterone before birth produced more tomboyish behaviour compared to those who didn't. E.g. they were more likely to spend time with other boys and be aggressive.
• What are the weaknesses for the hormonal explanation of gender

  they are correlational studies meaning that research lacks an independent variable so a cause and effect relationship cannot be established.

  
  

  many studies are animal studies so may not generalise to humans.

  
  

  expectations about the effect of hormones can act as confounding variables - eisenegger gave one group of women a placebo testosterone pill and kept the other group as a control. The results showed that during a bargaining game the group who were deceived into thinking they had taken testosterone behaved more competitively and unfairly.
• What are limitations of brain studies into gender


  Although some studies show differences between the brain structures of males and females, lots of other studies don't show these differences. Meaning the studies did not replicate. E.g. Janet Hyde conducted a meta analysis and found little to no difference between male and female brain structure.

  
  

  some studies have shown that there are bigger differences between SDN size and lateralisation within sexes compared to between male and female.

  
  

  research is socially sensitive

  
  

  cause and effect is hard to establish
• What are the strengths of the biological explanation for gender

  Case study - David Reimer

  
  

  born with XY chromosomes so biologically male. at aged 2 months, he was circumcised yet due to implications, his genitalia was damaged beyond repair. Psychologists advised a sex change surgery; believing gender is solely influenced by biology. Even after estrogen injections David did not identify as female, displaying male behaviour.

  
  

  This suggests that biology is greatly influential in explaining gender.

  
  

  Other studies found similar results adding reliability.