The roles of genes and hormones
- 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.
- ** = 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.
- AIS - ANDROGEN INSENSITIVITY DISORDER.
- 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.
- BATISTA FAMILY
- 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.
- The role of hormones can be studied by looking at individuals who have been exposed prenatally to abnormal hormone levels
- 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.
- Most gender development is governed by hormones
- 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
- in 1991 there was a ruling that genetic sex would no longer determine entry to the games
- Since 1968 genetic sex of all athletes was tested. AIS individuals couldn't compete.
- Shown in the dilemma faced by the international olympics committee.
- The importance of genetic factors
- 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
- The role of genes in gender development
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