chromosomes and hormones

• Identify the chromosomal structure

  males- XY

  females- XX
• Describe the role of chromosomes in sex and gender

  -Sex of a baby is determined at conception when the sperm and ovum form a zygote (fertilised egg)

  -Sperm and egg both contribute chromosomes to the zygote, the 23rd pair of which contains DNA instructions to determine the zygotes sex

  -Ovum can only supply an X chromosome while the sperm can contribute either an X or Y chromosome

  -If the sperm contributes a Y the zygote will be genetically male (XY)

  -if the sperm contributes a X the zygote will be genetically female (XX)

  -Male and female embryos up to 8 weeks have external genitalia that look the same

  -At 8 weeks, genetically male produce androgens which stimulate the development of male genitalia, in females this process odes not take place so female genitalia will develop

  -chromosmes also determine whether an individual has an endocrine system which is naturally testosterone- dominant (male) or oestrogen-dominant (female)

  -Chromosomes therefore determine someones biological sex
• What are hormones?


  Hormones are chemical substances secreted by glands throughout the body

  -carried in the bloodstream

  -Same sex hormones occur in both men and women but differ in amounts therefore the effect they have upon different arts of the body

  -considered to be responsible for the differences in gender
• Explain the role of testosterone in sex and gender

  -testosterone is the dominant sex hormone in male endocrine systems

  -it controls the development of the male sex organs and begins to be reduced at around 8 weeks of the foetal development when it is switched ins by the SRY gene on the Y chromosome

  -At puberty, increased testosterone triggers the development of secondary sex characteristics such as facial hair and the voice deepening

  -testosterone causes typically male behaviours such as aggression and a higher sex drive
• Explain the role of oestrogen in sex and gender

  -Oestrogen is the dominant sex hormone in female endocrine systems

  -in the womb, two X chromosomes cause ovaries to develop which leads to an oestrogen-dominant system

  -At puberty, it governs the development of secondary sex characteristics such as breast development and menstruation

  -Oestrogen also causes women to experience heightened emotionality and irritability during their menstrual cycle which is known as premenstrual tension (PMT)
• Explain the role of oxytocin in sex and gender

  -Sex hormone which promotes feelings of bonding, contentedness and calming

  -Important in breastfeeding as it also promotes lactation so that breastfeeding is possible and also reduces the levels of cortisol, the stress hormone

  -Women are known to have more oxytocin than men

  -plays an important role in childbirth, as it causes contractions, enables lactation, and assists with mother child bonding

  -However, both sexes release equal amounts of oxytocin during sexual intercourse
• A03- SUPPORT RESEARCH- hormones responsible for gender differences

  -E.g. More testosterone is thought to cause higher levels of aggression, more physical strength and a higher sex drive

  -Van Goozen et al who studies transgender individuals who were undergoing hormone replacement therapy; taking hormones of the opposite sex

  -Found that transgender women who were taking oestrogen showed decreases in aggression and visual-spatial skills while transgender men who were taking testosterone showed the opposite

  -Suggests that hormones play a significant role in developing gendered traits
• A03- SUPPORT RESEARCH- Influence of testosterone

  -Christina Wang et al.

  -Researched male hypogonadism- a conditon which causes a mans testes to fail to produce normal levels of testosterone

  -by giving 227 hypogandal men testosterone therapy for 180 days

  -improved their sexual function, libido and mood, and increased muscle strength

  -indicates that testosterone has a strong influence on sex and gender
• A03- Strength - effects of testosterone in animals

  -Young (1966) gave testosterone to female rats and oestrogen to male rats, and found that they showed reversed sex behaviours

  -Female rats attempting to mount the males and the males presenting themselves to be mounted

  -this suggests that hormones play a powerful role in gendered behaviour

  -however this piece of research may not be applicable to humans as there are key biological differences between the two species

  -As human sexuality is much more complex in humans, unlike rats, engage in sexual activity for pleasure as well as for procreation
• A03-Challenging evidence- hormones have no effect on gendered behaviour

  -Tricker et al carried out a double blind study where 43 males were given either weekly injections of testosterone or placebo (the control group)

  -it was found that there was no significant differences in aggression between the two groups after a ten week period

  -this means that the increased aggression in transgender or hypogonadal men seen in the aforementioned studies may have actually been due to placebo effect or other factors

  -research is not fully conclusive
• A03- Limitation- emphasising the role of hormones on sex and gender

  -exaggerate the importance of nature

  -If it was found that gender identity was solely down biology, wo would expect to find many more differences in male and female behaviour than there are currently and for all males/females to be more similar than they are

  -it would also mean that gendered behaviours would be consistent across all cultures but a study by Margaret Mead found that this was not the case

  -She found that variety in gendered behaviours in Papua New Guinea which differs from our Western expectations

  -In Arapesh tribe there were little differences between how men and women behaved. whereas in Tchambuli tribe, women were more dominant and violent while men were more dependent on them

  -this may prompt other explanations such as the social learning theory - to point to the importance of social context when learning our gender identity and roles which would explain cross cultural differences