Sexual Orientation Flashcards
which sex has a larger genetic contribution to one’s sexual orientation
males - females have a smaller genetic contribution
what is the genetic contribution for MZ twins for sexual orientaiton?
it is not 1 - indicates that there is an effect of the environment
what did Micheal and Zucker’s gay/lesbian RETROspective study indicate?
lesbian and gays had a higher recall of cross-sex typed childhood behaviours compared to straight children
(81%lesbians & 89% gays)
what was Green’s prospective study? and the results
examined feminine and control boy children
most of the ‘feminine’ boys turned out gay - 0% of the control boys turned out gay
what was Zucker and Bradley’s PROspective study? and the results (boys)
examined 55 boys with gender dysphoria
more ended up identifying as gay etc - not straight
overall, what can prospective studies tell us? (gays)
there are differences at childhood between individuals that identify as gay or straight
what can lesbian prospective studies tell us?
more girls with gender dysphoria end up identifying as lesbian than straight.
(btw - more men are diagnosed with gender dysphoria than women)
Estrogen (DES) and lesbianism - what are the facts
DES is a synthetic oestrogen that is related to sexual orientation in offspring
Mums who took DES had offspring with higher tendencies for attraction to women (lesbian)
overall DES disrupts the typical fetus environment which correlates to differences in development
experiment by Ward
shows that stressed mother releases an adrenaline related hormone (Similar to testosterone) which binds to the receptors in the brain that would have been receiving testonsterone
= effects fetal environment
stress is consistent with…
gay babies
what did Domer/ Schenk etc find?
larger number of bisexual/ gay men born during and after world warII
Ellis’ mice experiment -
mice were exposed to prenatal stress - alcohol = more likely to have gay/ lesbian offspring
also found that maternal nicotine use is linked to an increase in male offspring being gay
how does mothers who were psychologically stressed, affect sexual orientation?
mothers who were psychologically stressed were more likely to give birth to male children who were gay
more maternal stress =
increased likelihood of offspring being gay/ bisexual
increased oestrogen =
changes in sexual orientation
sexual orientation is related to the – and the way the –specifically –
brain , brain evolves, the environment in the womb (hormones)
what does stress do to the mileu hormone?
it disrupts this typical sex hormone (mileu) in the fetus in the 1st and possibly 2nd trimester – leading to deviations form the norm
Manning’s research -
about 1 in 7 gay men owe their sexual orientation to their birth order
- the more older brothers a man has, the greater chance they have of being gay (older sisters make no difference and chance is not the same for lesbians)
do older brother’s affect the offspring’s chance of being gay if they are left handed?
no
Tell me about Blanchard’s research - gay men/ birth order (antibodies…)
- Mother has an immune response - increases antibodies against a protein that is only made in males (NLGN4Y) - as she has never seen the things on the male chromosome
- Antibodies build up in mothers’ blood with each male son that is born (immune response)
- NLGN4Y produced on the surface of brain cells, making it relatively easy for antibodies to find and detect it
what is the ordering of the amount of antibodies found in women after pregnancy?
women who have no sons < women who have straight sons < women who have gay sons
(less to more antibodies)
what is the protein NLGN4Y thought to play a role in?
in how brain cells connect to each other so it could affect brain structures that moderate attraction
- mother’s immune response may alter typical function of these brain structures
Fruit flies
– sexual orientation comes down to connection strength between synapses in the brain - similar mechanism to humans?
what does DNA methylation do?
activates/ deactivates genes
it changes the way the body and brain develop - for some reason binds to receptors in male fetus brain.
explain male fetus and testosterone…
- 8weeks testes produce testosterone which changes the way the body and brain develops
- If testosterone doesn’t get a chance to bind to receptors in brain, then their sexual orientation changes – gay.
(Stress hormone may also cause this )
are there both environmental and genetic links to sexual orientation?
yes
- there may be a genetic potential to be gay/ straight but an environmental trigger can activate/ deactivate the gene
tell me about brain lateralisation and sexual orientation
(savic and lindstrom)
gay men and straight women = no difference in brain volume between left/ right half
lesbian women and straight men = right side is bigger
why - brain lateralisation for sexual orientation
(Geschund and Galaburda)
fetal testosterone compromises the development of the left hemisphere and facilitates the right hemisphere functioning
describe the fruit flies experiment
GB gene suppresses synapse strength - stronger synapses make fruit flies process sex pheromones differently
Pheromone applied to dead wild type male = increased courting behaviour in GB mutant fly
any drug that strengthens synapses leads to similar behaviour in non-gb mutant flies
why are sheep more similar to humans than fruit flies - relating to sexual orientation?
sexuality is controlled by the hypothalamus in humans and sheep
8% of rams prefer to root other rams rather than ewes - which is similar % of gay men - humans
what is the gay sheep experiment?
(Roselli & Stormshank)
- small area in hypothalamus (MPOA/AH) controls mate preference in sheep
the volume of (MPOA/AH) is controlled by exposure to testosterone and estradiol around the time of birth
injecting testosterone increases the volume of female oSDN - part of the MPOA/AH
which changes the way the hypothalamus is developed - relating to sexual orientation
why would same sex attraction be selected for in evolution if same sex couple produce fewer children?
(Zietsch et al)
because same genes that produce same-sex behaviour also produces some degree of non-sterotypical personality characteristics
research also shows that females are attracted to men that are kind/ considerate etc…
so the idea is that males might be more successful if they have genes that predispose them to this
fecundity?
is the ability to reproduce
female relatives of gay men have increased fecundity
homophobia study
(Adams et al)
showed significant difference in arousal of homophobic men - more aroused by gay porn
associated with discomfort of one’s feelings of same-sex attraction
what does DES do?
acts as estrogen (synthetic estogren) -disrupts the typical fetus environment which correlates to differences in development
what is a broad overall changes of changes in sexual development?
a disruption/ change in the fetal environment
- such as mother’s stress, drugs/alcohol, antibodies etc