Sexual determination during embryogenesis is a very delicate procedure. If even as little as one rececptor on a cell is damaged or missing the proper chemical signals cannot be given the cells. In these cases what should have been a boy is now a girl or something in between (depends on when during embryogenesis the problem occured). Medicine used to turn these intersexed individuals into girls. However, often the brain is not that of a girl but a boy or visa versa. So today medicine prefers to the leave the intersexed child alone and see which way the child goes, as we all know there are activities that relate to boys and those activites that relate to girls, especially when they are young.
I see many people here grouping the intersexed with the homosexual. The intersexed seriously were BORN that way. They cannot help it. Homosexuals make a choice. There's a difference.
Accurate in the sense of choice. On a genetic level it is one or the other. The incidence of such cases is only one in several thousands.
There is no "gay" gene.