The Role of Genes and Hormones
The role of genes in gender development
> Each person has 23 pairs of chromosomes in each cell of the body & these chromosomes carry hundreds of genes containing instructions about physical & behavioural characteristics (eye colour & predisposition to mental illness).
> 1 pair of chromosomes are called the sex chromosomes because they determine an individual's sex. XX chromosomes = female & XY chromosomes = male. Y carries little genetic material but does determine the sex.
> There's usually a direct link between an individual's chromosomal sex and their external & internal genitalia.
> During prenatal development all individuals start out the same (m & f embryos have external genitalia that look essentially feminine).
> When the foetus is 3 months old, if it develops as male, the testes usually produce the male hormone testosterone which causes external male genitalia to develop.
> Genetic transmission explains how individuals acquire their sex - it may also explain some aspects of gender because of the link between genes and genitalia and hormones.
The role of hormones in gender development
> Chromosomes initially determine a person's sex but most gender development is governed by hormones which are produced prenatally & in adolescence (puberty). These influence the development of genitalia & the brain (both influence gender behaviour).
Development of genitalia
> The role of hormones in gender development can be seen by studying individuals who have been exposed prenatally to abnormal hormone levels (intersex individuals).
> Normally external genitalia are in accord with genetic sex but in some cases a genetic male embryo is exposed to too little male hormone and the result is that the newborn appears externally female (AIS & Batista family).
> Genetic females may be exposed prenatally to too much male hormone & the result is ambiguous genitalia (swollen labia resembling a penis) - such girls are usually assigned girls at birth and are content with this gender.
> BERENBAUM AND BAILEY found that girls exposed prenatally to too much testosterone are often interested in male-type activities and are tomboyish, presumably due to the influence of the male hormones.
Sex differences explained -
> Male brains are different from female brains in…