But the claim is that their DNA is different. That’s why one is gay and the other is not, in almost all cases.
“But the claim is that their DNA is different. That’s why one is gay and the other is not, in almost all cases.”
Assume for the sake of discussion you have twins who appear to have genes which are expected or known to produce homosexual behavior in humans or human males. The assume in 30 percent of the cases in one study of such twins one of the two twins develops with heterosexual behavior. The heterosexual behavior in the twin with homosexual genes may be explained by two possible types of biochemical causes. First, the genes which determine homosexual behavior may not be turned on because other genes were not present or failed to function according to plan a consequence of other genetic factors. Second, epigenetic factors during gestation and/or in the postnatal development could interfere with the expression of the homosexual genes.
Conversely, you can have twins with heterosexual genes, yet on occasion have one of those twins who has other epigenetic alterations of the gene expressions not shared by the twin.
See:
Epigenetics
https://en.wikipedia.org/wiki/Epigenetics