Is there a gay gene?

Homosexuality has a strong genetic component. One study found that among fifty-six pairs of monozygotic male twins, concordance (simultaneous incidence) for homosexuality was 52 percent, while it was only 22 percent for fraternal (dizygotic) twins and 11 percent for unrelated adopted brothers. This indicates that the closer two males are genetically, the more likely they are to have the same sexual orientation. Several studies have pointed to a likely location for male homosexuality traits at the tip of the X chromosome. It should be noted that not all males with this sequence identified themselves as homosexual, and so it seems likely that a variety of factors (environmental and genetic) may have roles in determining sexual orientation. So far, there are no correlate statistics for female homosexuality.