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

how are genetic and hormonal explanations linked?

they are both connected- genes coordinate the levels of hormone in the body

how many chromsomes do we have?

46 (23 pairs)

what are chromosomes and where are they found?

Coiled up lengths of DNA molecules found in the nucleus

what do chromosomes do?

carry genetic information (genotype) that codes for physical and behavioural characteristics (phenotype)

what is the role of chromosomes in sex development?

-the 23rd chromosome pair determines biological sex

XY= male

XX= female

-sex chromosomes produce different hormones that control sex development

-for example, testes develop due to sex determining region on the Y chromosome and produce androgens that result in other differences

what is the role of chromosomes in gender development?

-genetic differences between biologically male and female chromosomes are thought to result in observable behavioural variations by coding for different neural structures and hormone levels

-these influence gender expression

what are hormones and where are they found?

biochemical messengers inside the bloodstream that influence the functioning of other bodily organs and systems

released from the glands

what is testosterone, and what is its role in both sex development and gender development?

-it is an androgen (male sex hormone), 10x more in males than females

-role in sex= involved in development of male foetus, testes and secondary sexual characteristics like big muscles in adulthood

-role in gender= linked to higher levels of aggression, a trait linked with masculinity

what is oestrogen, and what is its role in both sex development and gender development?

-it is a female sex hormone, found in much higher concentrations in women

-role in sex= regulates the menstrual cycle and development of secondary sexual characteristics

-role in gender= high levels after giving birth linked to maternal caregiving behaviour and reduction in levels is implicated in irritability and being emotional- more feminine trait

what is oxytocin, and what is its role in both sex development and gender development?

-hormone produced in both sexes, but higher in females

-role in sex= stimulates lactation in females, and key aspects of the reproductive system

-role in gender= triggers 'tend and befriend' and other caring/attachment behaviour in females, and pair bonding in both genders

RESEARCH STRENGTH: what evidence is there for the genetic explanation?

Van Beijsterveldt 2006

-collected childhood gender identity data from over 8000 MZ and DZ pairs in Netherlands

-found 70% of variance in gender identity was due to genetic factors- shows atypical gender development is heritable

-also showed that girls with female co-twins were more likely to show cross gender development than girls with male co-twins

^counters SLT, supports biological

RESEARCH STRENGTH: what animal research is there to support the influence of hormones?

Van Leengood 1987

-female rats stopped showing caring behaviour towards babies when given a drug to stop oxytocin

Wagner 1980

-male castrated mice reduced aggressive biting that returned to normal levels when injected with testosterone

-> suggests hormonal changes result in changes to sex-typed behaviour

RESEARCH STRENGTH: what evidence supports the role of biology?

Diamond and Sigmundson 1997

-reviewed case of 8 month old who lost penis during routine circumcision, and had a vagina reconstructed and was socialised to be a girl on reccommendation of a psychologist called Money

-initially she behaved in a feminine way, but lost interest and felt she had a masculine gender identity during puberty, and detransitioned on discover she was a biological male

-shows nature outweighed the effects of nurture

what are 2 limitations of Diamond and Sigmundson's research review?

the effects of nature outweighing nurture may be because of her identical twin brother being a role model

is an unusual case study- generalisable?

LIMITATION: what issues are there with animal studies used to support bio. explanations?

-generalisation to humans may not be valid as human experience is influenced by socialisation, culture and complex cognitive schema development, which is not present in most animals

STRENGTH: what is a benefit of animal studies?

-they allow for controlled experiments to show causal relationships that due to ethics could not be conducted on humans

STRENGTH: what are the practical applications of bio. explanation research?

-the understanding of how hormones influence gendered behaviour such as maternal behaviour can help in development of hormonal clinical treatments for parenting disorders, and treating heightened aggression

LIMITATION: why may labelling hormones 'male' and 'female' be an issue?

-they arent limited to effects in just one gender

-for example, a form of oestrogen called oestrodial is vital for male sexuality, as low levels lead to low sex drive and reduced ability to produce sperm

LIMITATION: why is cause and effect of hormone questioned?

-gender socialisation may be affecting hormone levels rather than the other way around

-Van Anders (2016)- testosterone levels significantly increased in women when doing a task that weilded power over another person

-suggests gender-> testosterone pathway, and that socialisation encourages men to be competitive, raising levels even more

-therefore just considering biology may be too simplistic, and social factors are needed for a more holistic, valid explanation

what are two examples of atypical sex chromosome patterns?

Klinefelter's syndrome

Turner Syndrome

what is Klinefelters syndrome, how many people does it affect, and what are two physical, physiological and psychological characteristics?

-where a biological male has an extra X chromosome- XXY

-1/660 males have it

-physical= long limbs, breast tissue

-physiological= reduced volume in amygdala, and increased in posterior-occipital lobe

-psychological= poorly developed language and reading skills, easy to distress

how is klinefelter's treated?

with testosterone therapy

what is Turner's syndrome, how many people does it affect, and what are two physical and psychological characteristics?

-where biological females have one less X chromosome- X0

-1/2000 women

-physical= no menstrual cycle, limited breast development

-psychological= high levels of reading/ writing skills, low visual ability, socially immature

how is Turner's syndrome treated?

oestrogen replacement therapy

what are two strengths of research into atypical sex chromosome patterns?

-has led to medical interventions that improve the lives of people with these conditions (increasing breast-development, increased reading skill)

-helps us understand typical patterns, and suggests gender has a biological basis

what is a limitation of research into atypical sex chromosome patterns?

-there may be a social influence that is being ignored in the development of these characteristics

-for example with Turner's syndrome, people are treated more childlike because of the way they look, encouraging the psychological characteristic of being socially immature