X Chromosome Again Linked to Homosexuality
Travis, John, Science News
In a reprise of the most controversial study of 1993, researchers surveying the genetic landscape of the X chromosome have discovered further evidence that it contains a gene or genes that may steer some men to homosexuality.
"Once again, we've found that more than half of gay brothers share the same chromosome region. It gives us additional confidence that there is something in this region involved in sexual orientation," says Dean H. Hamer of the National Cancer Institute in Bethesda, Md.
Two years ago, Hamer reported that men might inherit a predisposition to homosexuality through the X chromosome, whose genes are passed on by mothers (SN: 7/17/93, p.37). Some scientists harshly criticized the study, as well as the general effort to probe the genetics of behavior. This summer, the Chicago Tribune reported that a former member of Hamer's group had raised questions about how Hamer conducted the 1993 study, prompting a still-ongoing inquiry by the Department of Health and Human Services.
In the new study, as in the original, Hamer and his coworkers examined the X chromosomes of families that have two homosexual brothers. Since a son can inherit parts of his X chromosome from either of the two versions his mother has, the investigators looked for genetic markers, brief sequences of DNA, that differ between the two maternal X chromosomes.
Two-thirds of the 32 pairs of homosexual brothers included in the final analysis share the same markers for one portion of their X chromosome and thus inherited the same span, Hamer and his colleagues at the University of Colorado in Boulder and the Whitehead Institute for Biomedical Research in Cambridge, Mass., report in the November Nature Genetics.
Ordinarily, if that region played no role in sexual orientation, says Hamer, only about half the brothers would share it. …