Not necessarily. Some traits result from a combination of environmental and genetic factors. For example, someone might have a gene predisposing him to heart disease. But if he exercises and maintains a healthy weight, his heart might remain healthy throughout his life.
I am intrigued by the potential role of epigenetics in homosexuality. Epigenetics are modifications to the DNA which do not change genes, but do change gene expression (that is, how the body uses genes). If altered gene expression causes homosexuality, then controlling that gene expression and returning it to a normal state should cure the homosexuality.
It’s always seemed to me that male homosexuality is more hard-wired, by which I mean nothing more than it seems to have an early onset. Female homosexuality, on the other hand, often seems to be a reaction to negative heterosexual experiences later in life, more of a conscious choice.