OMIA:000393-37174 : Tetragametic chimerism (including Freemartin) in Ovis canadensis

In other species: taurine cattle , deer , pig , sheep , water buffalo , dog , horse

Categories: Reproductive system phene

Links to MONDO diseases: No links.

Mendelian trait/disorder: unknown

Considered a defect: yes

Cross-species summary: Tetragametic chimerism is a rare, sex chromosome disorder of sex development characterized by the two different haploid sets of maternal and paternal chromosomes and variable phenotype - from normal male or female genitalia, to different degrees of ambiguous genitalia, and often infertility. Also, in the cases of monochorionic dizygotic twins, it can be confined to blood of both twins. [ Orphanet : 199310 ] Freemartin or free-martin is an infertile female animal which is the twin of a male animal whose anti-Müllerian hormones affected its development in utero. Genetically the animals are chimeric (microchimerism, XX/XY leukocyte chimerism) - some stem cells from the male twin are received during in utero development via vascular connections between placentas. The condition is mostly reported in ruminants due to their multicotyledonary placenta type. Phene was renamed to 'Tetragametic chimerism' [16/11/2022]


1992 Kenny, D.E., Cambre, R.C., Frahm, M.W., Bunch, T.D. :
Freemartinism in a Captive Herd of Rocky Mountain Bighorn Sheep (Ovis canadensis) Journal of Wildlife Diseases 28:494-498, 1992. Pubmed reference: 1512891 .

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  • Created by Frank Nicholas on 06 Sep 2005