The role of chromosomes and hormones (testosterone, oestrogen and oxytocin) in sex and gender. Atypical sex chromosome patterns: Klinefelter’s syndrome and Turner’s syndrome

Biological Factors and Gender Development

AO1, Description:

The role of chromosomes

  • Chromosomes are made from DNA, there are 46 chromosomes in the human body arranges into 23 pairs. The 23rd pair determines biological sex.
  • The chromosomal structure for each gender is as follows – female (XX), Males (XY).
  • All normal egg cells produced by a human ovary have an X chromosome, half the sperm carry an X chromosome and half a Y. A baby’s sex is determined by the sperm that fertilises the egg.
  • The Y chromosome carries a gene called SRY, this causes testes to develop. The testes produce androgens (male sex hormones) which cause the embryo to become a male, without them it develops into a female.


The Role of Hormones – AO1, Description:

Chromosomes initially determine a person’s sex but most gender development actually comes about through the influence of hormones. In the womb, hormones act upon brain development and cause the development of reproductive organs. At puberty, a burst of hormonal activity triggers the development of secondary sexual characteristics.

You need to know about the role of 3 different hormones; testosterone, oestrogen and oxytocin.

Testosterone – Description, AO1

A predominantly male hormone (women also produce it, but at about 10% of the level found in males). Controls the development of male sex organs. Begins to be produced at around week 8 of gestation. Associated with the masculinisation of the brain, such as the development of specific areas like spatial skills, competativeness and aggressiveness.


Testosterone – Evaluation, AO3:


(1) Point: There is evidence of a link between testosterone levels and male-typical behaviours. Evidence: For example, Deady et al (2006) measured testosterone levels and gave the BSRI to women aged between 23 and 30, asking additional questions about maternal personality (e.g. the importance of having children, career, ambition). It was found that testosterone levels negatively correlated with low measures of maternal personality and reproductive ambition. Elaboration: This is a strength because it demonstrates that testosterone levels have an impact on the development of typical male and female behaviours, indicating that testosterone has a key role in the development of gender development.



(1) Point: Deady et al’s research was correlational. Example: For example, it is difficult to say in this study whether levels of testosterone impact on maternal personality and reproductive ambition or whether maternal personality and reproductive ambition impacts on levels of testosterone. Does having high levels of testosterone lead to low levels of reproductive ambition or does a low level of maternal ambition lead to higher levels of testosterone? Elaboration: This is a weakness because, it means that cause and effect cannot be established and therefore it becomes difficult to draw conclusions about the role of testosterone in gender development.

(2) Point: Deady et al’s research is socially sensitive. Example: For example, the research suggests that high levels of testosterone are more linked to masculinity traits (less maternal personality and reproductive ambition). This can be a particular sensitive topic as males tend to hold higher levels of testosterone suggesting that they are not natural carers/maternal. Elaboration This is a weakness because, the research can be seen as being discriminatory against males suggesting that because of their biological make up they are not programmed to be good caregivers, maternal and will have a lower ambition to reproduce. This often isn’t the case as males quite often display maternal characteristics and a willingness and want to reproduce suggesting that testosterone is not the only biological factor playing a part in the development of gender.


Oestrogen – Description, AO1:

  • A primarily female hormone (small amounts are produced in males)
  • Determines female sexual characteristics and menstruation
  • Responsible for both physical and emotional changes experience by women during their menstrual cycle (e.g. PMS)
  • Oestrogen plays a role in ‘feminising’ the brain, promoting neural interconnections for equal use of both hemispheres.


Oestrogen – Evaluation, AO3:


(1) Point: There is evidence of oestrogen being necessary for female-only behaviours. Evidence: For example, Albrecht & Pepe (1997) found that increasing oestrogen levels in pregnant baboons led to heightened cortisol production, which assisted the development of organs and tissues in foetuses. Elaboration: This is a strength because it demonstrates that oestrogen is necessary to pregnancy and for the growth of foetuses, a role that is exclusively fulfilled by women, indicating that oestrogen has a key role in gender/ sex related behaviours.


(2) Point: A strength of research into the role of oestrogen in the development of gender/sex related behaviours is that it uses scientific methods. For example, Albrecht and Pepe used scientific methods to measure levels of oestrogen and cortisol production (blood tests, saliva tests etc…) whilst also using scientific scanning methods to measure the development of the foetus. Elaboration: This is a strength because it means that the data collected in scientific and objective and can be used to draw firm conclusions about the role of oestrogen in the development of gender and sex related bahviours.



(1) Point: There are considerable objections to the idea of pre-menstrual syndrome (PMS) on the grounds that it stereotypes female experience. Evidence: For example, feminist writers claim that PMS is a social construction, not a biological ‘fact’ but a way of privileging certain groups over others, in this case men over women. Elaboration: This is a weakness because research into oestrogen and PMS appears to lead to the medicalisation of women’s lives (defined and treated as medical conditions) and ultimately the dismissal of women’s emotions, especially anger, by explaining them in biological terms.


Oxytocin – Description, AO1:

  • A hormone that also acts as a neurotransmitter, produced in the brain by both males and females to control key aspects of the reproductive system
  • Women produce much larger amounts of oxytocin than men, particularly as a result of giving birth, it stimulates lactation.
  • Oxytocin reduces the stress hormone cortisol and facilitates bonding, it’s referred to as the ‘love hormone’
  • Oxytocin is released in massive quantities during labour and makes new mothers feel ‘in love’ with their baby. This has fuelled the popular stereotype that men do not make ‘as good’ caregivers as women and are less interested in intimacy and closeness within a relationship.


Oxytocin – Evaluation, AO3:


(1) Point: There is evidence to suggest that there is a relationship between oxytocin and maternal behaviour. Evidence: For example, Van Leengoed et al (1987) injected an antagonist of oxytocin into female rats shortly after birth to inhibit oxytocin production. Mothers treated in this way showed a delay in maternal behaviours, such as picking up and grooming their pups. Normal maternal behaviour was seen when the antagonist wore off. Elaboration: This is a strength because the findings support the idea that oxytocin is involved in the promotion of maternal behaviour, supporting the link between the hormone oxytocin and gender development.



(1) Point: Much of the research into the role of hormones in sex and gender can be criticised for extrapolation. Evidence: For example, most of the research only investigates the influence of hormones on sex and gender in animals, therefore little is being discovered about how hormones impact sex and gender in humans. Elaboration: This is a weakness because the results of any animal research cannot be generalised beyond the experiment to humans because of differences in brain functioning and physiological development, this renders most of the research in this area as useless, which raises the question as to whether animal research should be conducted if it offers so little information as to human development.


(2) Point: A further weakness of research looking at the role of oxytocin in the development of gender is that the research focuses on animals and so therefore can be criticised on the grounds of animal ethics. Example: For example, due to the fact that many researchers operate under the premises of the ‘hierarchy of intelligence,’ it is assumed that it is right to research on animals in order to further our understanding of humans. In the case of gender development, it considered by some researchers ethical to research on animals in order to understand the role of oxytocin in the development of gender. Elaboration: This is a weakness because, many researchers opposing the use of animals in research see that using animals in an attempt to understand human behaviour is pointless. Research findings from animals cannot be extrapolated to humans, with this being the case, many question the point of using/harming/treating animals unethically in research – if the results don’t tell us anything exact about human behaviour then what was the point of conducting animal research in the first place?


Atypical Sex Chromosome Patterns – Klinefelter’s Syndrome

Description – AO1:

Atypical sex chromosomes – what are they? Any sex chromosome that deviates from the usual XX/XY formation, tend to be associated with distinct patterns of physical and psychological symptoms

  • It affects between 1/500 and 1/1000 men.
  • Individuals who are affected by this are biologically male, with an anatommical appearance of a male, with an additional X chromosome (XXY).
  • 2/3s of people who have Klinefelter’s syndrome are not aware of it, diagnosis often comes about accidentally during examination for an unrelated condition.


Physical Characteristics

1. Reduced body hair

2. Some breast development

3. ‘softening’ or ‘rounding’ of body contours

4. Long limbs

5. Underdeveloped genitals

6. Issues with coordination

7. More susceptible to breast cancer


Psychological Characteristics

1. Poorly developed language skills

2. Poor reading ability

3. Passive and shy

4. Lack of interest in sexual activity

5. Don’t respond well to stressful situations

6. May show problems with memory


Atypical Sex Chromosome Patterns – Turner’s Syndrome

  • It affects approximately 1/5000 women.
  • Individuals who are affected by this are biologically female, with an anatommical appearance of a female, though there is an absence of one of the two alloted X chromosomes (X0)
  • Women with Turner’s syndrome have 45 chromosomes rather than the usual 46.


Physical Characteristics

1. Do not have a menstrual period (ovaries fail to develop)

2. Broad ‘shield’ chest, breasts don’t develop

3. Low set ears

4. ‘webbed’ neck

5. Hips are not much bigger than waist

6. Pre-pubescent appearance


Psychological Characteristics

1. Higher than average reading ability

2. Poor performance on spatial, visual memory and mathematical tasks

3. Socially immature

4. Trouble relating to peers

5. Difficulty ‘fitting in’


Atypical Sex Chromosome Patterns – Evaluation, AO3


(1) Point: Research into patients with Klinefelter’s Syndrome and Turner’s Syndrome has seen a development of therapies to improve the quality and duration of their lives. Evidence: For example, treating stunted growth often seen with Turner’s Syndrome by the application of growth hormones and the treatment of Klinefelter’s Syndrome with testosterone, which has seen those with the condition develop a less passive nature. Elaboration: This is a strength because it shows that such research into gender in the field of psychology is having a positive effect on human experience. In addition, such research has allowed for symptoms of these disorders to be effectively treated.



(1) Point: There is some difficulty in establishing a conclusive cause and effect relationship between the chromosomal pattern and symptoms of TS and KS. Evidence: For example, social immaturity observed in females with Turner’s syndrome may arise from the fact that they are treated ‘immaturely’ by the people around them; parents, teachers etc may react to the pre-pubescent appearance of people with TS in a way that encourages immaturity (this could have an impact on their performance at school too). Elaboration: This is a weakness because it shows that it is wrong to assume that observed psychological and behavioural differences are due to nature when it may actually be that environmental and social influences are more responsible for the behavioural differences seen in these individuals.


(2) Point: There are issues in making assumptions about behaviours indicative of KS and TS being atypical. Evidence: For example, the idea that individuals with TS are socially immature is based on the idea that there is a typical level of maturity for females, and the idea that individuals with KS are shy and passive is based on the idea that shyness and passivity is not a typical behaviour for a male. Elaboration: This is a weakness because it means that some of the criteria for TS and KS can be seen to be subjective and requiring inaccurate independent judgement to make a diagnosis. A situation could arise when one individual would say that a person is very shy yet another individual would judge this person as not being shy at all, such subjectivity calls into question the accuracy of the diagnosis of KS and TS.