The role of genes and hormones

Each person has 23 chromosomes, each chromosome carries hundreds of genes containing instructions about physical and behavioural characteristics. One pair of chromosomes called the sex chromosomes determine and individual's sex, females = ** and males = XY. The Y chromosome carries very little genetic material although it does determine the sex of the child. There is usually a direct link between an individual's chromosomal sex and their external genitalia and internal genitalia. During prenatal development all individualsstart of the same, a ew weeks after conception both female and male embryos have external genitalia that look essentially female. When feotus is abiut 3 months, if it is to develop as a male, the testes normally produce the male hormone testosterone, causes theexternal male genitalia to develop. Genetic transmission explains how individuals acquire their sex. It may also explain some aspect of gender role because of the link between gene and genitalia and hormones. 

Androgens are male hormones. Some XY individuals have an insensitivity to such hormones, i.e. thier bodies' tissues do not respond to the effects of the hormone. In extreme cases the consequence is that no external male genitalia develop. Such individuals are usually identified as females at birth and raised as girls. 

Chromosomes initially determine a person's sex but most gender development is governed by hormones, produced both prenatally and in adolescence. 

Development of genitalia = role of hormones in gender development can be seen by studying individuals who have been exposed prenatally to abnormal hormone levels. Normally external genitalia are in accord with genetic sex. However, in some cases a genetic male embryo is exposed to little male hormone and the result is that the newborn appeats externally to be female - adrogen insensitivity hormone. Conversely, genetic females may be exposed prenatally to relatively large doses of male hormones. The result is ambiguous genitalia. Such individuals are usually identified as girls at birth and are usually content with their gender assignation, although research has indicates that they are often interested in male-type activities and are tomboyish, because of the influence of the male hormones. Brain development = sex differences - male brains are different from females, e.g. girls generally appear better at social skills tan boys. Geschwind and Galaburda suggested that such sex differences may be cause by effects of testosterone levels on developing brain. Male brain are exposed prenatally to more testosterone than female brains leading to the development of masculinised brain. If brain of genetic female is exposed to testosterone prenatally effects may be to masculinise brain. Animal studies - Quadagno et al. found that female monkeys who were deliberetly exposed to testosterone during pernatal development later engaged in more rough and tumble play then other females and were more aggressive. 

Money and Ehrhardt 1972, claimed that biological sex was not the main factor in gender development, argued that sex of rearing was much more important and recommended that intersex individuals could be successfully raised as either a boy or a girl. But the case of David Reimer did not support this. This outcome has been further supported by subsequent research, Reiner and Gearhart, studied 16 genetic males born with almost no external male genitalia. 2 were raised as males and remained as males. Remaining 14 were raised as females, and of these 8 reassigned themselves as males by the age of 16, suggesting that biological factors have a key role in gender development. Research methods - most evidence comes from case studies such as the David Reimer case or small samples of abnormal individuals. Therefore, studies cannot be generalised, so lacks population validity, as we cannot generalise from abnormal individuals to the wider 'normal' population.

Hormonal research into biological influences on gender has useful real life applications. Research into AIS such as that by Imperato McGinkey et al who reported that the individuals raised as girls changed gender following puberty as a result of high levels of testosterone produceds, has shown us that hormones have a determining influence on gender. The Olympic Committee due to greater awareness gained through psychological research in 1991 decided that it would revert its earlier ruling o f only allowing ** or XY individuals to compete. Now biological sex does not bar entry into the games.

The role of genes and hormones in gender development is deterministic. This is because it only considers the biological makeup of an individual when determining the sex of an individual. This biological approach suggests that our genes and hormones determines the sex we choice. For example if an individual has the sex chromosome ** they would be a female or if they hadXY chromosome they would be a male. This theory also suggests that most gender development is actually governed by hormones produced both prenatally and in adolescene. Although biological factors are important to gender development,there are other crucial factors that play a role in gender development. For example, Dessens et al. studied 250 genetic females who were prenatally exposed to high levels of androgens but still raised female. 95% were content with their female gender, with only 5% experiencing significant gender dysphoria. Therefore, sex rearing is a key factors other than biology than has a key role in determining the sex of an individual. Hence this approach is reductionist as it does not consider other factors that play a crucial part in one's gender development.

This biological approach raises the nature vs nurture debate. This approach is heavily based on the nature side of the nature vs nurture debate, as it suggests that it an individual's biological make-up, their genes and hormones that determines its sex. However, the social learning theory suggests that gendered behaviours can also be learnt by operant conditioning; this is where the child will receive direct reinforcement or punishment for their behaviour. This usually occurs in children when they are at school at do gender-inappropriate activities; for example, if a boy plays dressing up, he is likely to have other boys laugh at him which will be seen as a punishment. They will then learn not to participate in that type of behaviour again. or through vicarious reinforcement were a child would observe someone and copy that gender specific behaviour, and of that child is rewarded that behaviour is likely to be repeated. Therefore, suggesting that this approach is reductionist as it does not consider the nurture side of the nature vs nurture debate which also plays apart in gender development.