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Open Access Publications from the University of California

Extreme skewing of X chromosome inactivation in mothers of homosexual men

  • Author(s): Bocklandt, Sven
  • Horvath, Steve
  • Vilain, Eric
  • Hamer, Dean H
  • et al.

Human sexual preference is a sexually dimorphic trait with a substantial genetic component. Linkage of male sexual orientation to markers on the X chromosome has been reported in some families.

Here, we measured X chromosome inactivation ratios in 97 mothers of homosexual men and 103 age-matched control women without gay sons. The number of women with extreme skewing of X-inactivation was significantly higher in mothers of gay men (13/97=13%) compared to controls (4/103=4%) and increased in mothers with two or more gay sons (10/44=23%).

Our findings support a role for the X chromosome in regulating sexual orientation in a subgroup of gay men.

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