It is genes that affect a man's sexual orientation of being gay or straight, a new study has revealed.
Dr Michael Bailey of Northwestern University said, "Sexual orientation has nothing to do with choice. Our findings suggest there may be genes at play - we found evidence for two sets that affect whether a man is gay or straight."
DNA of 400 gay men was used for the study and it was revealed that genes on at least two chromosomes influenced whether a man was gay or straight. They found that two small areas on the male genome seem to be associated to sexuality.
Qazi Rhaman, a King's College London psychologist, said that up to 40 per cent of a person's sexual orientation is affected by genes and there is a probability that many genes are involved. But Dr Rhaman also said that people should not be afraid in associating homosexuality with genes.
Richard Lane of Stonewall said that while more research is needed to understand the causes behind homosexuality, there are some signs to show its link with genetics.
Last year, before these results were announced, Bailey's colleague Alan Sanders warned that the new results should not made a basis to find out about the sexual orientation of a person.
On the other hand, there are other studies that say conditions in the womb also affect a person's sexual orientation.
Researchers said, "Although this could one day lead to a pre-natal test for male sexual orientation, it would not be very accurate, as there are other factors that can influence the outcome."