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MALE HOMOSEXUALITY IS LINKED TO X CHROMOSOME.

How much of human behavior is genetic? This controversial question has recently been raised with regard to homosexuality, because of twin studies and reported structural differences in the brains of homosexuals (see Journal Watch accession number 910917008).

A team at the National Institutes of Health took family histories from 114 gay men and noted that the men tended to have gay relatives on the mother's side of the family, but not on the father's side. This tendency, confirmed in interviews with relatives, suggested a trait passed on by mothers exclusively, which in turn suggested a gene on the X chromosome. Using genetic mapping, the team found that a set of five genetic markers at the tip of the long arm of the X chromosome were identical in 33 of 40 pairs of homosexual brothers. This finding indicates with more than 99 percent certainty that a gene associated with homosexuality lies in that area of chromosome X.

Comment: This research should be easy to confirm or dispute. If a gene is identified, a host of questions arise: What is the function of this gene and the protein it encodes? How likely is a male carrying the gene to be homosexual, and what fraction of gay males carry it? Does the gene affect females? The race is on for the answers.

— ALK

Published in Journal Watch General Medicine August 6, 1993

Citation(s):

Hamer DH et al. A linkage between DNA markers on the X chromosome and male sexual orientation. Science 1993 Jul 16 261 321-327.

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