London - Scientists have ruled out the existence of a single so-called "gay gene".
The largest ever genetic study into sexuality found no evidence of DNA material that was entirely responsible for homosexuality.
It could overturn the findings of a theory based on a 1993 study that found a genetic marker more common in gay men.
Experts now say thousands of genes are involved in sexuality – and even then their influence may be no more than 25 percent.
The environment that people grow up in is likely to be more important than DNA. Researchers sequenced the genes of more than 470 000 people, principally taken from the UK Biobank genetic database and DNA testing website 23andMe.