For the first time, researchers looked at the complete genome – a person’s entire DNA code – for more than 1,000 gay men and compared it to genetic data from a similar number of heterosexual males.

They discovered that DNA was different for gay and straight men around the genes SLITRK5 and SLITRK6.

SLITRK6 is an important gene for brain development, and is particularly active in a region of the brain which includes the hypothalamus.