chromosomes

what determines your sex

your genes determine biological sex. They also determine the production of homones that effect your gender

how many pairs of chromosomes do humans have

23 pairs each carrying genes that control diffferent characteristics

which pair determines biological sex

the sex chromosomes X and Y on the 23rd pair

XX is female

XY is male

what are examples of sex hormones

testosterone, oestrogen, and oxytocin

what is the SRY gene

the sex determining region of the Y gene

controls if gonads become ovaries or testes
at around 6 weeks the SRY gene causes the gonads of the embryo to develop as testes

what is the effect of the SRY gene on hormones

as testes are developed at 6 weeks, testosterone is produced

this causes external male genitallia to develop and so XY feoteses have higher levels of testosterone particularly between 8 and 24 weeks

what happens if the SRY gene is missing from the Y chromosome (or doesnt activate)

the foetus grows, is born, and lives as a little girl and later as a woman

she may have XY chromosomes, but these people are usually clearly women to themselves and everyone else

what is a controversial use of the discovery of the SRY gene

used as gender verification in the Olympic games, athletes with an SRY gene were not permitted to participate as females

what is genetic transmission

explains how individuals acquire their sex, may also explain some aspects of gender, due to the link between genes, genitalia and hormones

what is testosterone

a steroid hormone that stimulates the development of male secondary sexual characteristics

how present is testosterone in males vs females

predominantly found in males, but females also produce testosterone, with about 10% of the amount found in males

what are the gonads

sex glands, originally identical in XY and XX embryos, however in XY, genetic info on the Y chromosome means they become testes and produce hoemones inclusing the primary adrogen- testosterone

what is the second change in testosterone levels

after birth there is a surge in males which makes testosterone higher in males for about the first 6 months

what effects does testosterone have when released

development of male sex organs

acts on the hypothalamus as without this the brain develops as a female type

associated with masculanisation of the brain eg development of areas linked to spatial tasks

associated with malee type behaviours eg competitiveness and aggressiveness

what is a difference in the hypothalamus between males and females

the sexual dimorphic nucleus is bigger in males

believed to be due to the action of sex hormones

what is the role of oestrogen prenatally

as the default gender is famle, a feotus will develop as a female unless exposed to testosterone

females do not need hormones to direct prenatal genital development

but prenatally oestrogen may lead to a smaller brain size

what is oestrogen

a steroid hormone which plays a major role from puberty onwards promoting secondary sexual characteristics

it is primarily a female hormone, but small amounts are produced in males

what are the effects of oestrogen

psychological effects- premestural tension PMT- emotionality, irritability and irrational behaviour

directs the mestural cycle

diminishing levels are associated with the menopause

feminisation of the brain preomoting neural interconnections for a more ‘distributed’ female brain

female type behaviours eg sensitivity and co-operation

what is oxytocin

a polypeptide hormone which also acts as a neurotransmitter

has been called the love hormone as it promotes feelings of bonding in both men and women

where is oxytocin produced

the pituitary gland

what is the role of oxytocin

evokes feelings of conentment and calmness

greater action in females as it synergises (combines) with oestrogen to enhnace the effects of both

helps to facilitate childbirth and beastfeeding

increases 5x during sex but drops rapidly in men

affects female social behaviour eg mate selection, nesting behaviour, monogamy, nurturing and protection of offspring

can dampen the fight or flight response leading to the tend and befriend response seen in females

AO3 for the role of chromosomes and hormones in sex and gender

John Monet may have been wrong in claiming that biological sex is not the main factor in gender development

research suggests that genes and hormones are not the whole story- other factors are important too

A classic case of abnormal gender development illustrates that culture also has an important role in gender development

A greater understanding of intersex conditions through psychological research has led to real world applications

the effects of testosterone on brain development have been confirmed in experimental work with animals

Human studies suggest the relationship between hormones and behaviour may be complicated

John Money may have been wrong in claiming that biological sex is not the main factor in gender development

He argued that sex of rearing was much more important and recommended that intersex individuals like david Reimer could be successfully raised as either gender. The case study intially supported his views but ultimately David showed a strong male identity despite being raised as a girl

This outcome has been further supported by subsequent research, for example, that of Reiner and Gearhart who studied 16 genetic males born with almost no penis. 2 were raised as males and remained males 14 were raised as females and 8 had reassigned as males by the age of 16

Such research suggests that biological factors do have a key role in gender development

research suggests that genes and hormones are not the whole story- other factors are important too

Genetic sex does not match external genitalia in cases of abnormal hormone exposure and even hormones themselves do not produce a simple formula for establishing gender

The eventual outcome for an individual appears to be a complex and unpredictable combination of genes, hormones, sex of rearing, and socialisation. The outcome is described as unpredictable because there do not seem to be any simple rules

For example, in cases of congenital adrenal hyperplasia (CAH) research appears to indicate that the gender assigned at birth seems to be accepted by some individuals but not others

Thus, gender development must in part be biologically determined (nature) but experience, personal qualities, and socialisation (nurture) also have a key role

A classic case of abnormal gender development illustrates that culture also has an important role in gender development

The case concerns the Batista family from the Dominican republic. 4 children were born with externaal female genitalia and raised as girls. The large amounts of testosterone produced during puberty caused their male genitalia to appear externally. They were genetically XY, but the external male genitalia had not appeared because of an inherited gene causing testosterone insensitivity. It is said that the ‘girls’ accepted their new male role without any difficulty. It has been suggested that the ease of transition from female to male highlights the importance of culture. In a community prepared to accept fluidity in gender roles it seemed easy to move between roles, something which is much more difficult in Western culture

This case not only illustrates the powerful effects of testosterone (a biological influence) but also shows cultural expectations have a role in shaping gender development

A greater understanding of intersex conditions through psychological research has led to real world applications

In the past, surgery was the norm for intersex conditions such as CAH in order to make the individual look more normal. Now, the intersex society of north america reccommends that babies with such conditions should be assigned a gender, but no surgery should take place until an individual can make an informed decision themselves

This shows hoe psychological research can contribute to improving people’s lives

The effects of testosterone on brain development have been confirmed in experimental work with animals

Quadagno et al found that female monkeys who were deliberately exposed to testosterone during prenatal development later engaged in more rough and tumble play and were more aggressive than other females

This supports the effects of testosterone on increasing masculine behaviour

However, it can be questioned if we can generalise from animal studies

Human studies suggest the relationship between hormones and behaviour is complex

In a study by Eisenegger et al women were observed playing a bargaining game- the women who believed that they had been given a does of testosterone behavied in a more unfair mannet than those who had believed they had been a given a neutral placebo- demonstrating the effect of expectations

This research suggests that hormones may influence brain development and behaviour but the relationship is not a simple one, and that expectations also seem to influence our behaviour

What are atypical sex chromosomes

Any combinations of sex chromosomes other than XX and XY

associated with a distinct pattern of physical and psychological symptoms

what are examples of atypical sex chromosome conditions

Klinefelter’s syndrome

Turner’s syndrome

What causes Klinefelter’s syndrome

males having an extra X chromosome (XXY)

what is the prevalence of Klinefelter’s syndrome

1 in 1000 males

but it is thought that around 2/3s of people with Klinefelter’s syndrome are not aware of it

what are the psychological characteristics of Klinefelter’s

small testes that produce insufficint amounts of testosterone

lack the ability to grow facial hair and pubic hair compared to a normal male

may be some breast development at puberty

long gangly limbs in ratio to their torso, taller than average with broader hips

problems with coordination/ clumsiness

succeptible to health conditions more common in women eg breast cancer

Often infertile

Psychological characteristics of Klinfelter’s syndrome

poorly developed language skills and reading ability and associated cognitive difficulties eg dyslexia

behaviourally passive compared to other males

tend to be shy and lack interest in sexual activity

tend not to respons well to stressful situations, a tendency to get upset/ depressed easily

what causes Turner syndrome

females having only one complete X chromosome (XO pattern)

The second X chromosome is either missing or incomplete

when does turners syndrome occur

at conception (often ends in miscarrige- 1/10 in first trimester are due to turner’s syndrome)

Physical characteristics of Turner’s syndrome

Do not have a menstural cycle- ovaries fail to develop and so are sterile/ infertile

dont develop breasts and so have a broad ‘shield’ chest

associated with low set ears

a short ‘webbed’ neck

shorter than average

may have downslanting eyes

lots of moles (

high waist:hip ratio as they have narrow hips

physically immature and retain the appearance of pre-pubescent girls

misshapen internal organs- especially the heart and kidneys

psychological characteristics of Turner’s syndrome

higher than average reading ability and high level of verbal/ language skill

performance on spatial visual memory and mathematical skills is lower than normal

socially immature and have trouble relating to peers and experience difficulty ‘fitting in’

AO3 for atypical sex chromosome patterns

Studies of people with atypical sex chromosome patterns are useful as they contribute to our understanding of the nature- nurture debate

There may be issues in leaping to the conclusion that innate ‘nature’ influences have a powerful effect on the psychology and behaviour

continues research into atypical sex chromosome patterns is likely to leas to earlier and more accurate diagnoses of Turner’s and Klinefelter’s syndromes as well as more positive outcomes for the future

Caution should always be exercised when drawing conclusions from an unusual and unrepresentative sample of people

Studies of people with atypical sex chromosome patterns are useful as they contribute to our understanding of the nature- nurture debate

By comparing people who have these conditions with chromosome- typical individuals, it becomes possible to see psychological and behavioural differences between the two groups eh higher verbal abilities for girls with Turner's syndrome

It may be logically inferred that these differences have a biological basis and are a direct result of the atypical chromosome structure. This would suggest that innate nature influences have a powerful effect on psychology and behaviour

there may be issues in leaping to the conclusion that innate nature influences have a powerful effect on psychology and behaviour

the relationship between the chromosomal abnormalities associated with Turner's and Klienefelters syndrome and the differences in behaviour for these individuals is not causal. Environmental and social influences may be more responsible for behavioural differences. For example, social immaturity associated with Turner's syndrome may arise from people around them treating them in this way due to physical appearance

This suggests it is wrong to assume that observed psychological and behavioural differences are due to nature

Continued research into atypical sex chromosome patterns is likely to lead to earlier and more accurate diagnosis and more positive outcomes for the future

Research has suggested that those who identified with Klinefelters syndrome and treated from a young age has significant benefits compared to those diagnosed later in life. For example testosterone replacement therapy can help people with Klinefelters syndrome increase their muscles, deepen the voice, and stimulate facial and body hair growth. Growth hormone injections beginning in early childhood may increase final adult height for those with Turner's syndrome by a few inches. Oestrogen replacement therapy starting at puberty can start breast development and progesterone started later can begin the monthly menstrual period to keep the womb healthy

This shows how research into atypical sex chromosome patterns has practical applications to treatment and the subsequent improvement of peoples lives

caution should always be exercised when drawing conclusions from an unrepresentative and unusual sample

the main issue is the lack of generalisability from atypical individuals to the wider population. Individuals who look different (due to atypical chromosomes) are unlikely to be treated in the same way as their peers. the generalisation is further limited by the fact that only 1/3 of those with Klinefelters are aware they have the condition so the samples are biased being only based on those who are diagnosed

These people may be different to those who havent been diagnosed in important physical and psychological ways. This may make it difficult to assess the relative contribution of nature and nurture in terms of behavioural and psychological differences between typical and atypical individuals