The findings, shared at the annual meeting of the American Association for the Advancement of Science in Chicago, revealed that in a study that tested the DNA of 409 gay men, at least two chromosomes may affect a man’s sexual orientation.
"Sexual orientation has nothing to do with choice. 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," said Michael Bailey of Northwestern University, who carried out the research.
The study involved drawing blood from 409 gay brothers and heterosexual members of their families. Analysis confirmed that an area on the X chromosome – which men inherit from their mothers -- known as Xq28 has some impact on sexual orientation. Another stretch of DNA on chromosome 8 also affects male sexual behavior, they said.
While the work has yet to be published, the findings confirm the results of a controversial study conducted in 1993 by Dean Hamer, a scientist at the U.S. National Cancer Institute.