Sexual Orientation

Question 1

which sex has a larger genetic contribution to one’s sexual orientation

Answer 1

males - females have a smaller genetic contribution

Question 2

what is the genetic contribution for MZ twins for sexual orientaiton?

Answer 2

it is not 1 - indicates that there is an effect of the environment

Question 3

what did Micheal and Zucker’s gay/lesbian RETROspective study indicate?

Answer 3

lesbian and gays had a higher recall of cross-sex typed childhood behaviours compared to straight children

(81%lesbians & 89% gays)

Question 4

what was Green’s prospective study? and the results

Answer 4

examined feminine and control boy children
most of the ‘feminine’ boys turned out gay - 0% of the control boys turned out gay

Question 5

what was Zucker and Bradley’s PROspective study? and the results (boys)

Answer 5

examined 55 boys with gender dysphoria
more ended up identifying as gay etc - not straight

Question 6

overall, what can prospective studies tell us? (gays)

Answer 6

there are differences at childhood between individuals that identify as gay or straight

Question 7

what can lesbian prospective studies tell us?

Answer 7

more girls with gender dysphoria end up identifying as lesbian than straight.
(btw - more men are diagnosed with gender dysphoria than women)

Question 8

Estrogen (DES) and lesbianism - what are the facts

Answer 8

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

Question 9

experiment by Ward

Answer 9

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

Question 10

stress is consistent with…

Answer 10

gay babies

Question 11

what did Domer/ Schenk etc find?

Answer 11

larger number of bisexual/ gay men born during and after world warII

Question 12

Ellis’ mice experiment -

Answer 12

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

Question 13

how does mothers who were psychologically stressed, affect sexual orientation?

Answer 13

mothers who were psychologically stressed were more likely to give birth to male children who were gay

Question 14

more maternal stress =

Answer 14

increased likelihood of offspring being gay/ bisexual

Question 15

increased oestrogen =

Answer 15

changes in sexual orientation

Question 16

sexual orientation is related to the – and the way the –specifically –

Answer 16

brain , brain evolves, the environment in the womb (hormones)

Question 17

what does stress do to the mileu hormone?

Answer 17

it disrupts this typical sex hormone (mileu) in the fetus in the 1st and possibly 2nd trimester – leading to deviations form the norm

Question 18

Manning’s research -

Answer 18

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)

Question 19

do older brother’s affect the offspring’s chance of being gay if they are left handed?

Answer 19

no

Question 20

Tell me about Blanchard’s research - gay men/ birth order (antibodies…)

Answer 20

1. 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
2. Antibodies build up in mothers’ blood with each male son that is born (immune response)
3. NLGN4Y produced on the surface of brain cells, making it relatively easy for antibodies to find and detect it

Question 21

what is the ordering of the amount of antibodies found in women after pregnancy?

Answer 21

women who have no sons < women who have straight sons < women who have gay sons
(less to more antibodies)

Question 22

what is the protein NLGN4Y thought to play a role in?

Answer 22

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

Question 23

Fruit flies

Answer 23

– sexual orientation comes down to connection strength between synapses in the brain - similar mechanism to humans?

Question 24

what does DNA methylation do?

Answer 24

activates/ deactivates genes
it changes the way the body and brain develop - for some reason binds to receptors in male fetus brain.

Question 25

explain male fetus and testosterone…

Answer 25

1. 8weeks testes produce testosterone which changes the way the body and brain develops
2. 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 )

Question 26

are there both environmental and genetic links to sexual orientation?

Answer 26

yes
- there may be a genetic potential to be gay/ straight but an environmental trigger can activate/ deactivate the gene

Question 27

tell me about brain lateralisation and sexual orientation
(savic and lindstrom)

Answer 27

gay men and straight women = no difference in brain volume between left/ right half

lesbian women and straight men = right side is bigger

Question 28

why - brain lateralisation for sexual orientation
(Geschund and Galaburda)

Answer 28

fetal testosterone compromises the development of the left hemisphere and facilitates the right hemisphere functioning

Question 29

describe the fruit flies experiment

Answer 29

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

Question 30

why are sheep more similar to humans than fruit flies - relating to sexual orientation?

Answer 30

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

Question 31

what is the gay sheep experiment?
(Roselli & Stormshank)

Answer 31

• 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

Question 32

why would same sex attraction be selected for in evolution if same sex couple produce fewer children?
(Zietsch et al)

Answer 32

because same genes that produce same-sex behaviour also produces some degree of non-sterotypical personality characteristics

Question 33

research also shows that females are attracted to men that are kind/ considerate etc…

Answer 33

so the idea is that males might be more successful if they have genes that predispose them to this

Question 34

fecundity?

Answer 34

is the ability to reproduce

female relatives of gay men have increased fecundity

Question 35

homophobia study
(Adams et al)

Answer 35

showed significant difference in arousal of homophobic men - more aroused by gay porn

associated with discomfort of one’s feelings of same-sex attraction

Question 36

what does DES do?

Answer 36

acts as estrogen (synthetic estogren) -disrupts the typical fetus environment which correlates to differences in development

Question 37

what is a broad overall changes of changes in sexual development?

Answer 37

a disruption/ change in the fetal environment
- such as mother’s stress, drugs/alcohol, antibodies etc