role of chromosomes and hormones in sex & gender

• Genetic factors


  Chromosomes and hormones that cause gender differences in behaviour
• Gender and sex


  • Interrelated
  • Any differences in gender are due to physiology (nature)
• Females


  Inherit 2 X sex chromosomes, one from each parent (XX sex chromosome pattern)
• Males


  Inherit an X chromosome from their mother and a Y chromosome from their father (XY sex chromosome pattern)
• Differences in sex chromosome patterns

  Leads to differences in behaviour
• SRY gene on the Y chromosome

  Confers male sexual characteristics (e.g. development of testes) through production of androgens, especially testosterone
• Prenatal stage (before the child is born)

  1. Release of testosterone establishes male circuits in the brain

  2. Absence of testosterone develops feminised circuits
• As a result of these brain differences, males and females are born with a predisposition towards masculinity and femininity
• Testosterone


  Linked to behavioural effects of aggression
• Female sex hormones oestrogen and progesterone


  Linked to personality traits e.g. high levels of oestrogen are believed to lead to heightened emotionality and irritability
• Women


  Typically produce more oxytocin than men
• Oxytocin facilitates bonding which has fuelled the stereotype that men are less intimate and nurturing than women
• There is animal research to support the hormonal explanation of gender
• Male rat castrated at birth and given oestrogen injection in adulthood


  Exhibits female sexual behaviour when tested with male rat
• Female rat injected with testosterone during infancy and given testosterone injection in adulthood


  Shows male sexual behaviour when tested with female rat
• Strength of the study

  • The results suggest that the rats' sexual behaviour is strongly influenced by hormones
• There is research to support the effect of hormones and chromosomes on behaviour
• Imperato-McGinley et al (1978) studied the Batista family from the Dominican Republic

  • Four of the children had XY chromosomal make up but were identified as girls at birth because they appeared to have female genitalia
  • They were raised as females until puberty when the release of dihydrotestosterone led to the sudden development of male genitals
  • The little 'girls' grew up to be muscular men and had no difficulty in adopting the male gender despite being reared as girls
• This case study


  • Suggests that chromosomes and hormones (nature) have a stronger effect than nurture (upbringing) on gender identity