Linkage between sexual orientation and chromosome Xq28 in males but not in females

Abstract

We have extended our analysis of the role of the long arm of the X chromosome (Xq28) in sexual orientation by DNA linkage analyses of two newly ascertained series of families that contained either two gay brothers or two lesbian sisters as well as heterosexual siblings. Linkage between the Xq28 markers and sexual orientation was detected for the gay male families but not for the lesbian families or for families that failed to meet defined inclusion criteria for the study of sex-linked sexual orientation. Our results corroborate the previously reported linkage between Xq28 and male homosexuality in selected kinships and suggest that this region contains a locus that influences individual variations in sexual orientation in men but not in women.

Sexual orientation related differences in spatial memory

“…Homosexual males and females show robust sexatypical shifts in retrospective and prospective childhood play interests and behavior and gender role orientation, and there is strong evidence to show similar shifts in cognitive functioning, neuroanatomical variation in hypothalamic and callosal regions, and neurophysiological activity in homosexual males (Alexander & Sufka, 1993;Bailey & Zucker, 1995;LeVay, 1991;Lippa, 2000;Sanders & Ross-Field, 1987;Reite et al, 1995;Scamvougeras et al, 1994). Genetic and prenatal hormonal factors are viewed as critical in the ontogenesis of these differences and for homosexual partner preferences (Hu et al, 1995;McFadden & Pasanen, 1998;Williams et al, 2000). Prenatal hormonal manipulations in animal models also affect aspects of spatial memory performance.…”

A Review of Xq28 and the Effect on Homosexuality

“…In addition to using homosexual sibling pairs, this study sampled heterosexual brothers to see if they had similar linkages in the Xq28 region. The results demonstrated that 67% of the homosexual pairs and only 22% of the heterosexual pairs shared any Xlinked connection (Hu et al, 1995). Even though this confirms that heterosexual males lack certain Xq28 regions, the sample sizes were smaller, using only 32 homosexual pairs and 11 heterosexual pairs.…”

“…The results demonstrated no significant sharing of Xq28 markers in both heterosexual and homosexual sibling pairs (Hu et al, 1995). Within the study itself, there was acknowledgement that although this likely indicates different mechanisms for females, the sample sizes were too limited to make a more definitive statement (Hu et al, 1995). Another explanation for the findings is that the Xq28 locus might be recessive in females signifying that female homosexuality may not be influenced by sex-linked genes (Hu et al, 1995).…”

“…This study was also the first to attempt and find similar outcomes in females. The results demonstrated no significant sharing of Xq28 markers in both heterosexual and homosexual sibling pairs (Hu et al, 1995). Within the study itself, there was acknowledgement that although this likely indicates different mechanisms for females, the sample sizes were too limited to make a more definitive statement (Hu et al, 1995).…”

Genetic basis of male sexual behavior

“…Family studies have suggested that homosexual orientation may be subject to a degree of heritability in both males and females. Detailed linkage analysis within families with multiple male homosexual members revealed that the male homosexual trait tended to be sex-linked and correlated with inheritance of polymorphic DNA markers from the chromosomal region Xq28 (Hamer et al, 1993;Hu et al, 1995). Female homosexuality showed no such correlation.…”