The roles of genes and hormones

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  • Created by: Kelsie
  • Created on: 27-05-14 12:10
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  • Gender
    • The role of genes in gender development
      • Everyone has 23 pairs of chromosomes; they carry 100s of genes containing physical/behavioural characteristics (e.g. eye colour/predisposition to certain mental disorders
      • Sex chromosomes = determines individuals sex.
        • XX = female
        • XY = male
        • Direct link between sex chromosome + external/internal genitalia.
      • During prenatal development individuals start out the same. A few weeks after conception all embryos have external female genitalia.
        • If the embryo is meant to be XY, (at 3 months) testes begin to produce testosterone which causes male genitalia to grow.
      • Genetic transition = explains how we acquire our sex + may also explain a individuals sense of whether they're male/female because of the link between genes, genitalia + hormones.
        • Androgens (e.g. testosterone) are male hormones
        • Some XY (intended males) have an insensitivity to these hormones = their bodies don't respond to the hormone
        • In extreme cases no external genitalia develops
          • In these cases, XY individuals may be recognised as female at birth and raised as a girl.
          • Dominican Republic
          • 4 children born with external female genitalia + raised as girls
          • At puberty, large amounts of testosterone produced + male genitalia appeared.
          • Children were XY but due to inherited gene that causes AIS, the correct genitalia didn't appear
          • The girls accepted change without difficulty
            • This may be because they had never taken on feminine roles + a number of relatives had similar experiences so they expected to become males.
    • The role of hormones in gender development
      • Most gender development is governed by hormones
        • These are produced prenatally (e.g. testosterone) and adolescence (e.g. a surge of hormones during puberty leads to secondary sexual characteristics)
      • Hormones influence development of genitalia and/or affect the development of the brain, both influence gender behaviour
      • Development of genitalia
        • The role of hormones can be studied by looking at individuals who have been exposed prenatally to abnormal hormone levels
          • Intersex individuals
        • Normally external genitalia are in accord with genetic sex (e.g. a genetic male develops a penis)
          • However, sometimes a genetic male embryo is exposed too little to male hormone = the newborn appears to be externally female (AIS + BATISTA FAMILY)
        • Genetic females may be exposed prenatally to large doses of male hormones
          • e.g. when mothers have been given drugs containing male hormones
          • Berenbaum+ Bailey said such individuals are usually identified as girls at birth and are content. They indicated they are usually interested in male-type activities + are tomboyish because of the influence of male hormones.
      • Brain development
        • Hoag: Male brains are different to female brains - girls appear better at social skills + boys are better at spatial navigation
        • Geschwind + Galaburda suggested that sex differences may be caused by the effects of testosterone levels on the developing brain.
          • Male brains are exposed prenatally to testosterone which leads to the development of a masculinised brain
          • If the brain of a genetic female is exposed to more testosterone the effect may also be to masculinise the brain.
        • Effects of testosterone on brain development have been confirmed in non-human animals
          • Quadagno found that female monkeys exposed to testosterone during prenatal development later engaged in more rough + tumble play and were more aggressive
        • Could explain why David Reimer 'felt' he was a boy even though he was raised as a girl due to a botched circumcision.
    • Commentary
      • The importance of genetic factors
        • John Money claimed biological sex was not the main factor in gender development.
        • Sex of rearing was more important. Intersex individuals (e.g. David Reimer) could be raised as either sex
          • David Reimer didn't support this
        • Reiner + Gearhart studied16 genetic males born with almost no penis
          • 2 were raised as males and remained males.
          • 14 were raised as females; 8 reassigned as males by 16.
          • Biological factors have a key role in gender development
      • Real-world application
        • Shown in the dilemma faced by the international olympics committee.
          • Since 1968 genetic sex of all athletes was tested. AIS individuals couldn't compete.
            • in 1991 there was a ruling that genetic sex would no longer determine entry to the games
              • Individuals are only excluded from women's events if they are physically male
    • Research Methods: much evidence comes from case studies or small samples of abnormal individuals.
      • Main issues is lack of generalisability from abnormal individuals to the 'wider normal'population
      • Intersexes may be more vulnerable to social influences because their biological ambiguities mean they have to search harder for clues to their identity
        • Another reason why research lacks generalisability


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