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Dominant Black (Coat colour K-Locus Dog)

The base colour of the dog is determined by the interaction of the the K locus (BlacK), A locus (Agouti) and the E locus (Extension). The alleles of these loci determine if and where the pigment eumelanin (black colour) and the pigment phaeomelanin (red colour) can be produced and how these two are distributed over the body.

 

The K locus has different alleles which determine if and where the pigment phaeomelanin can be produced in addition to eumelanin.

General Information

The K locus has different alleles which determine if and where the pigment phaeomelanin can be produced in addition to eumelanin.

 

  1. The KB allele is dominantly inherited and codes for a black coat colour, pheomelanin (red/light colour) cannot be produced.
  2. The kbr allele is inherited recessively and codes for the pattern "Brindle", pheomelanin can be produced at some areas.
  3. The ky allele is inherited recessively and allows the production of pheomelanin, which can be produced all over the body.

 

Impact of/on other Loci:

 

  • A-locus: The KB allele for dominant black suppresses the agouti locus. For the agouti colours to be visible in the phenotype, the ky/ky genotype must be present on the K locus or, for them to be partially visible (Brindle), the kbr/kbr genotype.
  • E-locus: The pigment eumelanin (black colour) must be produced (E/E or E/e) so that the expressions of the alleles of the K-locus are visible in the phenotype. Dogs with the light base colour (e/e) can be carriers for the K alleles, but these are not visible in the phenotype.
  • B-locus: Dominant black can be lightened to the colour "Brown" by the b-allele of the B-locus.
  • D-locus: Dominant black can be diluted to the colour "Blue/Silver" by the d-allele of the D-locus.

Genotype and Lab Report

Inheritance: autosomal-dominant

→ Animals with one or two copies of the gene (KB/kbr, KB/ky, KB/KB) show the phenotype dominant black. In animals with no copy of the gene, phaeomelanin can be produced.

 

Genotypes

 

KB/KB = Two copies for Dominant Black

The colour dominant black is expressed, the dog is black.

 

KB/kbr, KB/ky = One copy for Dominant Black

The colour dominant black is expressed, the dog is black.

 

kbr/kbr, ky/ky = No copy for Dominant Black

No variant for dominant black, pheomelanin can be produced on the whole body (ky/ky) or in partial areas (kbr/kbr).

Appearance

Dominant Black

 

Phaeomelanin (red/light colour) cannot be produced, the dog is completely black. The colour occurs in many breeds, e.g. Hovawart and Labrador Retriever.

 

Possible genotypes:

  • KB/KB
  • KB/ky

Test Information

Locus Information: K-Locus: KB-Allel

This test detects a deletion of 3 base pairs in the CBD103 gene, which causes "dominant black". However, this test cannot be used to test for the Brindle pattern kbr/kbr. Go to shop

Literature

  • Candille, SI., Kaelin, CB., Cattanach, BM., Yu, B., Thompson, DA., Nix, MA., Kerns, JA., Schmutz, SM., Millhauser, GL., Barsh, GS.: A beta-Defensin Mutation Causes Black Coat Color in Domestic Dogs. Science 318:1418-23, 2007. Pubmed reference: 17947548. DOI: 10.1126/science.1147880
  • Further information is available at Online Mendelian Inheritance in Animals.
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