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

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

Categories: Reproductive system phene

Mendelian trait/disorder: unknown

Considered a defect: yes

Cross-species summary: This is a type of sex chromosome difference of sexual development (DSD). Tetragametic chimerism is a rare, sex chromosome difference 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. [updated from 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]

Cite this entry

Nicholas, F. W., Tammen, I., & Sydney Informatics Hub. (2005). OMIA:000393-37174: Online Mendelian Inheritance in Animals (OMIA) [dataset].


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). J Wildl Dis 28:494-8, 1992. Pubmed reference: 1512891. DOI: 10.7589/0090-3558-28.3.494.

Edit History

  • Created by Frank Nicholas on 06 Sep 2005