If there is nothing genetically different about gay people then the only thing that signifies a difference is their behaviour. Gay people are gay when they say they are and when they do the things that show them to be gay. Likewise, perhaps, people are trans when they say they are, and no outward sign – or any biological signifier – need be there in the trans case any more than it is expected (or demanded) in the case of being gay.
Interesting point
