These days you can find a medical article to support anything-Remember that always!
The thing with homosexuality is is that...if it were genetic, then those genes should die out because homosexuals cannot reproduce. Thus those genes should have become extinct a long time ago.
In biology, we learn that the "survival of the fittest" of depends on how many offspring they can give their genes too. Homosexuals can't pass there genes to anyone, and thus that provides a large hurdle in any gene theory of homosexuals.
But you could argue that we have down syndrome babies, and they don't reproduce, yet we still have them. Unlike Down syndrome, there are no OBVIOUS chromosomal abnormaliteis in homosexuals-- and if there were they would come across a multitude of other problems, as DS babies do. Chromosomal abnormalities are normally pretty serious, you get lots of problems along with it. Plus in Down Syndrome there is a clear mechanism on why it is chromosome 21, at a certain maternal age that it occurs...With homosexuals that is yet to be elucidated, and or that it even is genetic has limited support.
What about the ones that are homosexual but get married to the opposite sex to reproduce, but still sleep with the same sex. There are plenty of cases of these that have come up, where the gay husband gets HIV from his partner and passes it on to his wife.
If it were genetic that would explain how the homosexual genes have not died out.