Last time I checked, we had not stopped identifying what all of our DNA does yet. We don't know there is no "gay gene". Not that it matters anyhow.
Look, homosexuality is not a choice. I realize it makes you feels better about being against homosexuality, but there is just no logical reason whatsoever to believe it. Look at all the people who committ suicide for being gay when they could instead just "choose" to become straight instead.