Coat color - dogs

Introduction into coat color in dogs

The colour of the fur coat of various animals depends on their descent. In the course of dog domestication, people bred a great number of dogs of various sizes and anatomy with bright coat colours that would make the survival in the wild nature impossible. They would be easily detected by predators and would be an easy prey for something else. On the other side, due to their brightly coloured coat they would not be able to hunt, as they would be quickly detected by a potential prey. The breed standard clearly defines for all purebred dogs what colour of coat is required, acceptable or unacceptable. Certain colours are a feature for exclusion from the breed as they are connected with undesired effects (on health, bright colours of hunting dogs, etc.).

The coat colour in dogs is influenced by production of two main pigments, eumelanin (brown to black) and phaeomelanin (yellow to brown-black or red pigment). In relation to the coat colour in dogs, several genes have been identified, for example MC1R (Melanocortin 1 receptor), CBD103 (beta-defensin 103), ASIP (Agouti signal peptide), TYRP1 (Tyrosin related protein 1) and others.  The initial overview:

MC1R - locus EM - alelle E, e, EM

CBD103 - locus K - alelle KB > kbr > ky

ASIP - locus A - alelle A, a

TYRP1 - locus B - alelle B, bs, bc, bd

MLPH - locus D - alelle D, d

In most mammals, the synthesis of eumelanin or phaeomelanin is regulated by two key genes MC1R and ASIP, and a third gene CBD103 plays an important role in domesticated dogs. The role of this gen has not been recognised until recently (Kerns et al., Candille et al.). This gen shows high affinity for MC1R and influences the control of pigment production.

In the coat colour inheritance, there has been described the hierarchy and mutual effects of the most important genes that influence the colour of a dog coat. The MC1R gene is epistatic to other genes responsible for the coat colour that means that this gene is able to block the expression of alleles of other locus, so that the trait required does not occur at all:

  • In case of presence of genotype e/e, the phaeomelanin pigment is produced and this pigment irrelevant of the genotypes of the other loci causes the resulting coat colour.
  • In case of genotype E/e or E/E, the locus K and locus A play an important role in the resulting colour.
    • Dark coat colour can be expected, if at least one allele KB (black allele) i.e.  potential genotypes  KB/KB, KB/ky, KB/kbr, is present
    • In case of presence of allele ky (yellow allele), i.e. genotypes ky/ ky, ky/ kbr or alelle kbr (brindle allele) responsible for fawn or dark brindle pattern (for example, in the breed of Staffordshire Terrier or Bendog), i.e. genotype kbr/ kbr, the locus A is responsible for the resulting coat colour:
      • In the presence of allele a (genotype a/a) the pigment eumalenin is produced (brown to black pigment),
      • In the presence of allele A (genotypes A/a, A/A) the resulting colour is affected by production of phaeomelanin pigment (light cream to brown-red or red pigment) or the coat has a brindle pattern, if at least one allele kbr (brindle) is present simultaneously..

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The diagram below shows the above system of allele hierarchy causing the coat colouring in dogs:

Coat-Colour-Inheritance-Dogs

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For more information about the individual loci determining the coat colour in dogs, see: