Testicular Feminization Syndrome (TFS), an X-linked recessive trait

    TFS is associated with an Androgen Receptor locus on the long arm of the X chromosome (Xq11-q12). The individuals have the XY karyotype typical of males, but develop physically and psycho-sexually as typical females. Development of some secondary sex characteristics (e.g., enlargement of the breasts) may be unimpaired, but axillary and pubic hair are typically absent. Individuals with TFS are often diagnosed only when they fail to menstruate at puberty. TFS appears to be due to an inability of tissues to respond to androgen.  Persons with TFS are invariably sterile, with a blind vagina, underdeveloped uterus, and sometimes rudimentary testes. Consequently, the TFS allele is not passed on by XY "male" individuals, but by their asymptomatic heterozygous XX sisters.

     Institution of gender testing in international athletic competition, beginning at the 1968 Olympic Games, was intended to identify male athletes attempting to "pass" as female after having undergone hormone treatment. No such individuals were detected, however women with TFS and an XY karyotype who therefore "tested negative" for Barr Bodies were routinely identified, and in some cases deprived of their medals. This goes to general questions of LGBT persons in sport.
