Technically their mental illness isnt hereditary though. Most research that even the genetic component of homosexuality is still dependent on the environment (No one is born gay, but some may be predisposed to it). If it were hereditary, it would have already been selected out of the gene pool, but it hasnt been, even in the animal kingdom. I dont knwo about trannies being heridtary though, as they are something completely different than gays in actuality. They are much more similar to schizos.