Certain genes may correlate to male sexual orientation, according to a study led by two Northwestern professors.

Dr. Alan Sanders, director of the Behavior Genetics Unit at NorthShore University HealthSystem, along with psychology Prof. Michael Bailey and other colleagues, tested the DNA of 409 pairs of gay brothers and their family members. Bailey explained they were not looking for specific genes that influence homosexuality.

“Rather, we looked for something called genetic linkage,” he said. “In genetic linkage studies, you look for relatively large segments of DNA, parts of chromosomes that contain many genes that are linked to the traits of interest.”

Results showed that part of the X chromosome, known as Xq28, was shared most often among the gay brothers. This supports a controversial paper published in 1993 by geneticist Dean Hamer, who also suggested there was a gene on the X chromosome relating to male sexual orientation.

Bailey said this replication of findings is scientifically important because Hamer’s study was, in retrospect, too small to allow for confident conclusions.

“I would say that we produced evidence consistent with these past findings, but I would not say we have nailed the case,” Bailey said.

To further solidify conclusions, a newer type of study will be necessary. Genetic linkage studies are now outdated, since the study was funded in the early 2000s but was not publicized until now, Bailey said. He and his colleagues have collected enough DNA from both gay and straight subjects to conduct a genome-wide association study, Bailey said.  This will allow them to get closer to a particular gene. 

The study is still being considered for publication in a scientific journal. No similar results have yet been found regarding female sexual orientation. 

Such research has implications for recent legislation in Uganda that gives life sentences for homosexual behavior. Bailey said he has been approached numerous times about what his study could mean for that law. The Ugandan government has challenged scientists to prove that homosexuality is genetically determined, rather than a choice. Bailey said the study’s actual replication of past findings is important scientifically, but it is less clear to him whether or not it should hold social or moral weight.

“I will say that in my very strong opinion, homosexuality has no bad consequences, or at least is no worse than heterosexuality,” Bailey said. “Homosexual people deserve their human rights.”

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