Genetics, Sexual Orientation and Gender Identity

human genome

complete set of nucleic acid sequences encoded as DNA within the 23 chromosome pairs

deoxyribonucleic acid

carries genetic instructions necessary for development, functioning, growth and reproduction

base pairs

3bil base pairs

99% are identical for all people

1% explains individual difs in physical and psychological features

variations are found every 1000th base pair

gene

unit of dna that codes for a protein

alleles

variants of genes that cause differently shaped or amounts of proteins

large scale genetic variation

chromosomal abnormalities e.g. change in number or arrangement

medium scale genetic variation

copy number variations- sections of dna are duplicated or deleted

insertions/deletions- nucleotides are added or removed from dna

small scale genetic variation

single base change- one nucleotide base is altered in dna sequence

heritability

measure of the extent to which differences in peoples genes account for differences in traits

polygenic

human traits are polygenic- many genes of a small effect size increase the likelihood of a trait developing

heritability of same sex behaviour (Langstrom et al 2020)

20-40% of individual difs in sexual behaviour are accounted by genetic differences

‘gay gene’ Ganna et al 2019

underlying genetics of same sex behaviour is complex

many genes contribute to individual differences in predisposition to same sex beh

=cannot predict based on genes

explanation for heritable same sex beh

genes may influence sense of smell and sensitivity to male hormones

sexual orientation may be better thought of as a continuum

Heritability of gender identity (Polderman et al 2018)

moderate to strong heritability of gender identity

but lack of molecular genetic evidence and poor understanding of environmental factors e.g. intrauterine hormonal factors

ethical considerations (Nuffield)

risk of findings being misused for employment, insurance, education policies

medicalisation of traits labelled as disorders

could support modern eugenics movements

lack of diversity in populations studied and researchers

should behavioural genetics research be stopped?

findings dont have direct policy implications, heritability of anything can lead to different arguments- Plomin

implications

gene therapies/ medicine to change genes to modify peoples behaviour

pre-natal selection- only for serious diseases

behavioural research needs

diverse researchers, ppts and research questions

rigour and replication before policies

engagement with lived experiences