I have a question about homosexuality in genetics?

Question

If homosexuality were caused by a gene, wouldn't one expect bisexuality to be as common as two different colored eyes? I realize I must be missing something, or the whole world would have realized this.

Answer 1

It's very unlikely that it's caused by "a gene" with simple dominance and recessiveness. Bisexuality is very common, although most people (especially men) find it easier to just "go with" the acceptable coupling. It may be that heterosexuality, homosexuality, and bisexuality are all influenced by different sets of genes. No one really knows.
Two different-colored eyes (heterochromia) is very uncommon in people, so I'm not sure where you're going with that.

Answer 2

Male homosexuality runs in families and so there is speculation that it may be largely genetic. Male homosexuals have 1/3 as many children as male heterosexuals, and so it is not too surprising that any alleles for homosexuality would be in the minority in a population. The question is why natural selection hasn't weeded it out more than it has. In short, science does not know the answer...it has been speculated that mothers of male homosexuals, who are themselves carriers of male homosexuality, may be at some selective advantage but we don't know what that is. One final point, female homosexuality is poorly studied but it appears to be less genetically determined and is completely unrelated to male homosexuality. Famiies that have lots of male homosexual members don't necessarily have more lesbian members and vice versa.

Answer 3

Are you proposing that one of the man's nuts would be straight and the other gay? It doesn't work that way, and yes, youi're missing something.

In fact, research has shown that true bisexuality is more common in women than in men. Men tend to be either straight or gay, but far less frequently truly bisexual.