Research confirms 'gay gene' discovery

The scientist who two years ago controversially announced the discovery of the "gay gene" has found further evidence for its existence in homosexual men but not in lesbian women.

Dean Hamer, a geneticist at the US National Cancer Institute in Washington DC, said yesterday that his latest research confounds the critics who called his earlier work into question.

A proclivity for homosexuality which some men carry on the X chromosome they inherit from their mothers is confirmed by the latest work, published in Nature Genetics, Dr Hamer said. "You can never say we're 100 per cent sure but we're twice as sure as before. We are better than 99 per cent sure that it's not a fluke."

Dr Hamer, working this time with a team from the University of Colorado and the Whitehead Institute in Cambridge, Massachusetts, extended his earlier study of gay brothers to include heterosexual brothers and lesbian sisters.

Although the scientists found genetic "markers" that werelinked to whether a man was gay, they did not find the same markers in lesbian women. This is hardly surprising as male and female sexuality is very different, Dr Hamer said.

Dr Hamer refused to answer questions on allegations he is under investigation by the US government's Office of Research Integrity, which examines suggestions of scientific misconduct. "You'd have to speak to my lawyers. All I can say is that the main findings of the earlier work have never been challenged."

In the latest study, Dr Hamer analysed the genetic material of 33 pairs of gay brothers and 11 pairs of heterosexual brothers. He reproduced the results of the earlier work by finding that genetic traits on a region of the X chromosome were more likely to be shared by gay men, suggesting this part of the chromosome is involved in sexual orientation.

But Dr Hamer said it was far from certain that any man who inherits the "gay gene" will become homosexual.