Panel of genetic tests for the main coat colour genes of the horse, applicable to all breeds. It determines the genotype at the classic loci governing the distribution of eumelanin (black) and phaeomelanin (red), with the E locus (MC1R) and the A locus (ASIP) as the basis of the panel and, in many panels, other dilution and modification loci. It allows prediction of the expected colours in the offspring of a given mating. It is not a disease test: it provides information on coat phenotype and inheritance.

Applies to all equine breeds. The allele frequencies of each locus vary enormously between breeds: some alleles are fixed in particular breeds and absent in others, which makes genotyping especially useful in crosses between lines with different coats.

- It does not produce clinical signs: these are variants that affect the coat phenotype\n- Changes in the proportion and distribution of eumelanin and phaeomelanin in hair and skin\n- Predictable phenotypes in the offspring from the genotype of the parents\n- Possible combinations masked by epistasis (for example, chestnut over the A locus)

Classical genetics in the early 20th century established the behaviour of the extension locus (E) and the agouti locus (A) in the horse from experimental crosses. In 1996, Marklund and co-workers identified the p.Ser83Phe mutation of MC1R responsible for the chestnut colour (PMID 8995760). In 2001, Rieder and co-workers characterised the ASIP variants that distinguish bay from black horses (PMID 11353392). The e^a allele of MC1R (p.Asp84Asn) was described by Wagner and Reissmann in 2000 (PMID 11086549). Subsequently other loci (cream, grey, dun, silver and others) were added to the panel, and today coat genotyping is a routine tool in breeders' associations.

- Use the E/e and A/a genotypes of the parents to calculate the expected colours of each mating\n- Remember that e is recessive: E/e carriers do not show chestnut in their coat and are only detected by DNA\n- Take epistasis into account: an e/e homozygote (chestnut) hides its genotype at the A locus\n- Combine the panel with other dilution loci from the laboratory if you are looking for specific coats\n- Do not prioritise coat over health, functional or temperament criteria in selection

Always interpret the result together with the other loci in the panel: dilutions such as cream, dun or silver and progressive grey can mask base phenotypes. Coat genotyping is a phenotype and registration tool: do not extrapolate it to health conclusions or to the animal's sporting aptitude.

1. Marklund L, Moller MJ, Sandberg K, Andersson L. A missense mutation in the gene for melanocyte-stimulating hormone receptor (MC1R) is associated with the chestnut coat color in horses. Mamm Genome 1996;7(12):895-9. PMID: 8995760
2. Rieder S, Taourit S, Mariat D, et al. Mutations in the agouti (ASIP), the extension (MC1R), and the brown (TYRP1) loci and their association to coat color phenotypes in horses (Equus caballus). Mamm Genome 2001;12(6):450-5. PMID: 11353392
3. Wagner HJ, Reissmann M. New polymorphism detected in the horse MC1R gene. Anim Genet 2000;31(4):289-90. PMID: 11086549
4. OMIA:001199-9796 (MC1R) y OMIA:000201-9796 (ASIP). https://omia.org/OMIA001199/9796/ · https://omia.org/OMIA000201/9796/