If there actually was a homosexual gene,(for those claiming to be born that way), I would be against abortion of that potential queer. If there was a maniacal tyrant or murderer gene(like Hitler, Stalin, Jeffery Dahmer, etc.) I would be against the abortion of the potential killer.
BTW, EVERY Down Syndrome person I have ever known is a real sweetheart.
There is no "homosexual gene," nor is there a "murderer gene." What there seems to be are genes that predispose people to become homosexuals or psychopaths. Not all people with this genetic predisposition become homosexuals or psychopaths, and not all psychopaths become violent criminals (many become successful and upwardly mobile if ruthless professionals - Steve Jobs had all the hallmarks of a sociopath/psychopath).