OMIA:000393-9796 : Tetragametic chimerism (including Freemartin) in Equus caballus (horse)

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

Categories: Reproductive system phene

Links to MONDO diseases: No links.

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]

Genetic engineering: Unknown
Have human generated variants been created, e.g. through genetic engineering and gene editing

Cite this entry

Nicholas, F. W., Tammen, I., & Sydney Informatics Hub. (2023). OMIA:000393-9796: Online Mendelian Inheritance in Animals (OMIA) [dataset].


2023 Demyda-Peyrás, S., Laseca, N., Anaya, G., Kij-Mitka, B., Molina, A., Karlau, A., Valera, M. :
Prevalence of sex-related chromosomal abnormalities in a large cohort of Spanish purebred horses. Animals (Basel) 13:539, 2023. Pubmed reference: 36766428. DOI: 10.3390/ani13030539.

Edit History

  • Created by Imke Tammen2 on 15 Feb 2023