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A female animal, usually a calf, that is born as the twin of a male animal and is sterile because of having abnormal internal reproductive organs.
freemartina female twin born with a male, in which normal female sexual development has been adversely affected by hormones produced by the male twin.
a sterile female born co-twin with a male. Occurs most commonly in cattle, very rarely in sheep, and apparently not at all in the other species. Male hormones produced by the male calf share the common circulation and inhibit the normal development of genitalia of the female. The female is also an erythrocytic chimera and can be diagnosed as a freemartin by this means. It can also be diagnosed by cytogenetic techniques. It produces white cells with XY as well as cells with XX chromosomes. Structural changes of nonpatent vagina, small vulva, cordlike uterus and hypoplastic ovaries are diagnostic but inconsistent. Some freemartins are quite normal clinically but all are sterile.