G-d doesn't make junk.
While I don't bellieve there is a "gay gene" either, there may, in some cases, be a predisposition toward homosexuality that may have a genetic component; however, whether or not to act on it is a matter of choice. Many people are born with a predisposition toward alcoholism, but nowhere in scripture does that give anybody license to be a drunk. Paul said that we all have our crosses to bear. Mine is that if I eat half of what a normal person eats, I gain weight. It doesn't give me an excuse to be a glutton. The alcoholic has to be careful about exposure to alcohol and someone with homesexual tendencies needs to be more cautious in same sex friendships. It doesn't mean it's easy, but I don't remember reading anywhere in scripture that life is easy.
**G-d doesn't make junk.**
There are deformities in nature, and people are born with genetically inherited sicknesses and deformities.
However, even if a 'gay gene' did exist, it would only be a fraction of homosexuals with it, and it doesn't mean that any resulting homosexual behaviour should be acceptable or promoted as such.