By Kate Kelland

LONDON (Reuters) – A large scientific study into the biological basis of sexual behavior has confirmed there is no single “gay gene” but that a complex mix of genetics and environment affects whether a person has same-sex sexual partners.

The research, which analyzed data on DNA and sexual experiences from almost half a million people, found there are thousands of genetic variants linked to same-sex sexual behavior, most with very small effects.

Five of the genetic markers were “significantly” associated with same-sex behavior, the researchers said, but even these are far from being predictive of a person’s sexual preferences.

“We scanned the entire human genome and found a handful – five to be precise – of locations that are clearly associated with whether a person reports in engaging in same-sex sexual behavior,” said Andrea Ganna, a biologist at the Institute of Molecular Medicine in Finland who co-led…