Test Detail

Canine solid coats (black, brown-chocolate)

Dermatológico · Dog

A set of dog coat pigmentation traits, not a disease. 'Solid black' (K locus) and 'brown/chocolate' (B locus) are two independent traits. The K locus (CBD103 gene) regulates eumelanin production and determines whether the coat is solid black; the B locus (TYRP1 gene) determines brown/chocolate versus black colouration. The test makes it possible to know each breeding animal's alleles and predict offspring colours.
Inheritance patternMendelian trait. K locus (CBD103) with allele hierarchy KB > kbr > ky; the KB allele (solid black) is dominant. B locus (TYRP1) of autosomal recessive inheritance: two b alleles (b/b) are required for the brown/chocolate coat.
Gene / MutationK locus (CBD103): 3-bp deletion in exon 2 predicting an in-frame deletion of a glycine (ΔG23); KB allele (dominant black), together with kbr (brindle) and ky (OMIA:001416-9615). B locus (TYRP1): variants b^s (stop codon Q331ter, exon 5), b^d (deletion of Pro345, exon 5) and b^c (S41C, exon 2) (OMIA:001249-9615); b^h has also been described in the Siberian Husky.
PenetranceThe concept of disease penetrance does not apply: the effect on colour depends on the genotype, but the final coat phenotype results from interaction with other loci (for example A/agouti and E/extension). Therefore the K and B genotype alone does not predict the animal's entire colour.
Codevtwu
Turnaround time20 days
Price55,86 €

Incidence

Multi-breed canine panel: covers the B locus (brown/chocolate) and the associated nose/liver. No universal allele frequencies are published; they vary greatly by breed, line and country and must not be extrapolated.

Breeder management

- It is a coat-colour test: it must not be used to cull breeding animals on health grounds\n- Interpret K and B together with the other pigmentation loci (A, E) to predict the colour of the offspring\n- Inform breeders that being a carrier of b or ky does not imply disease\n- Do not mate based only on colour if there are other priority health traits in the breed

Specialist notes

It is not a pathology. The K locus (CBD103) determines solid black/brindle/permit agouti; the B locus (TYRP1) determines brown versus black. The result must be interpreted in the context of the rest of the pigmentation genotype and not as a clinical diagnosis.

References

1. Candille SI et al. 2007. A beta-defensin mutation causes black coat color in domestic dogs. Science. PMID: 17947548
2. Schmutz SM et al. 2002. TYRP1 and MC1R genotypes and their effects on coat color in dogs. Mammalian Genome. PMID: 12140685
3. Van Buren SL et al. 2021. A novel TYRP1 mutation associated with brown coat color in Siberian huskies. Animal Genetics. PMID: 33421162
4. OMIA:001416-9615. Coat colour, dominant black. Online Mendelian Inheritance in Animals.
5. OMIA:001249-9615. Coat colour, brown, TYRP1-related. Online Mendelian Inheritance in Animals.

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