The role of chromosomes and hormones

• Chromosomes


  Collections of DNA in the nucleus of cells. Humans have 23 pairs of chromosomes and the 23rd pair determines biological sex
• Females - XX
• Males - XY
• All human eggs have an X chromosome. Half the sperm have an X chromosome and half have a Y chromosomes. When a sperm fertilises an egg, the resulting embryo will be XY or XX
• Y chromosome carries a gene called "sex-determining region Y" (SRY) which causes testes to develop in an XY embryo and androgens to be released. These masculinise the embryo so it develops as a male. Absence of androgens, embryo develops into a female
• Testosterone


  Masculinises the brain of XY embryos. Leads to greater development of brain areas with spatial skills. Associated with male type behaviours such as competitiveness and aggression
• Oestrogen


  Female sex hormone that determines female sexual characteristics. Involved in controlling the menstrual cycle. Also associated with female type behaviours such as sensitivity and cooperation
• Oxytocin


  Referred to as the love hormone, as it is involved in bonding and is released during hugging, kissing and sex. Females produce more oxytocin than males as it plays a role in childbirth and breastfeeding.

  Males producing less oxytocin supports the stereotype that males are less interested in intimacy in relationships
• + Evidence to support the role of hormones

  Van Goozen et al studied transgenders undergoing hormone treatment

  • Transgender women (Male-Female) receiving oestrogen injections showed decreases in aggression and visuo-spatial skills
  • Transgender men (Female-Male) who were being injected with testosterone showed the opposite

  Shows testosterone and oestrogen have some influence on gender related behaviours
• -Explaining gender in terms of chromosomes and hormones oversimplifies a complex concept

  Biological model takes a reductionist approach when explaining gender - Reduces behaviour down to the lowest possible level of explanation and ignores other factors such as media or cognitive processes that affect gender development

  More holistic approach would be a biosocial explanation. Argues whilst sex is biologically determined, the socialisation we recieve will determine our gender identity. Takes into account importance of childhood and socialisation as well as bio factors
• -Chromosomes and hormones overemphasise the role of nature in gender development


  If gender identity was down to bio we would expect similar gender stereotypes universally. However a cross-cultural difference is found

  • Mead studied male and female behaviours in 3 different tribes
  • (1) males and females both showed non-aggressive, gentle behaviour. (2) both were "Masculine" (3)Females in control

  Shows gender is socially constructed and is influenced by nurture as behaviours were different. Also the world do share some stereotypical behaviours so we can't put too much emphasis on minorities
• +Complete Androgen Insensitivity Syndrome (CAIS)


  With CAIS, have XY chromosomes but external genitals are female. But no womb or ovaries. XY chromosome in formed with testes and testosterone but body doesn't respond, so foetus develops a female body with female hormones

  Supports role of hormones, chromosomes are XY but many people will keep a female gender identity so oestrogen is important for feminisation and testosterone important for masculinisation
• Atypical sex chromosomes

  Sex chromosomes that differ from the usual XX or XY. These patterns are associated with distinct physical and psychological symptoms
• Klinefelter's syndrome


  Affect biological males who have an extra X chromosome (XXY)
• Klinefelter's syndrome physical characteristics: Reduced body hair, some breast development at puberty, underdeveloped genitals, long gangly limbs and the rounding of body contours
• Klinefelter's syndrome psychological characteristics: Poorly developed language skills, poor reading ability, lack of interest in sexual activity, memory problems and solving issues and inability to respond well to stress
• Turner's syndrome


  Affects biological females who are missing an X chromosome (XO)
• Turner's syndrome physical characteristics: No menstrual cycle as ovaries fail to develop, no breast development, broad chest, low set ears, high wast:hip ratio, retain pre-pubescent appearance
• Turner's syndrome psychological characteristics: Higher than average reading ability, low spatial and visual memory, socially immature and experience difficulty fitting in
• + Research into atypical sex chromosome patterns have had practical applications


  Continued research means those suffering with Klinefelter's and Turner's syndrome will be diagnosed earlier and more accurately. Herlihy et al studied 87 people with Klinefelter's syndrome and found those diagnosed early and treated early had significant health benefits compared to those diagnosed in adulthood. More accurate diagnosis early in life means positive outcomes so is a strength
• -Research into atypical sex chromosomes involved studying those who are unrepresentative of general population


  Only 1/3 with Klinefelter's are aware they have it. So those involved in research are those who have been diagnosed. They are likely to be at the more severe end of the scale in terms of symptoms so may not be representative of most people with the syndrome, limiting generalisations
• + Research into atypical sex chromosomes have contributed to nature v nurture debate


  By comparing those with these conditions and chromosome typical people we are able to see psychological and behavioural differences between the two groups. Could be inferred these differences have a biological basis and are a result of the abnormal chromosomal structure. Suggests innate influences have a powerful effect on psychology and behaviour, supporting nature
• -Cautious in drawing conclusions around atypical chromosomes being down to nature


  Social immaturity found in girls with Turner's syndrome may be from the fact they are treated immaturely by people around them due to the pre-pubescent appearance. Could have an impact on their performance at school so cannot be sure how much of the characteristics are due to nature or nurture