New research by Chicago’s Northwestern University indicates that specific genes can increase the chance that a man will be homosexual.
Researchers studied the genetic makeup of 400 pairs of twins and found that those that were openly gay were more likely to share similarities in the Xq28 region of their X chromosome and also in Chromosome 8.
The researchers believe this shows that genetics is about 30 to 40% responsible for determining a man’s sexuality.
The rest, they believe, is determined by environmental factors such as a mother’s hormonal levels during pregnancy.
‘Sexual orientation has nothing to do with choice,’ researcher Professor Michael Bailey told The Times.
‘Our findings suggest there may be genes at play and we found evidence for two sets that affect whether a man is gay or straight.’
‘It is not completely determinative, there are certainly other environmental factors involved.’
However Hamer said that if someone tried to use these genes as a pre-natal test for homosexuality it would not be very accurate as the bigger picture was yet to be understood.
The region of the X chromosome that Professor Bailey found to be shared by gay men is the same that American geneticist Dean Hamer suggested was linked to homosexuality in 1993 – leading to it being dubbed ‘the Gay Gene.’
Corresponding genes for lesbians are yet to be identified.
Previous research has shown that gay and straight men’s brains are structurally different and that gay men’s brains respond to the sex pheromones produced by other men whereas heterosexual men’s brains respond to the sex pheromones produced by women.
The results come as Ugandan President has asked a team of scientists to investigate whether homosexuality is a choice before he will sign that country’s Anti-Homosexuality Bill.