D Locus – Dilution Dog Coat Color
Dilution dog coat color is controlled by genes of D locus. D locus contains a dilution gene, which is recessive, so the d gene is dilution and the D gene is non-dilution. This means that in order for the dog to be dilute it must be homozygous (dd genotype), and if it is heterozygous (Dd genotype) it will have normal, not diluted pigmentation.
The D locus dilution gene affects both eumelanin and phaeomelanin. Dilution dog coat color is characterized by a specific pigmentation phenotype. The specific pigmentation phenotype in dogs with coat colour dilution is caused by defective transport of melanosomes which leads to an accumulation of melanosomes around the melanocytes’ nuclei as well as large clumps of pigment in the hair shafts. When homozygous with a dilution gene, a black dog becomes blue and a liver dog becomes isabella. The gene affects also nose and eye colors. In blue dogs the nose will be blue pigmented and isabella dogs are slightly darker than liver. Eyes will lighten to amber.
This trait is inherited as a Mendelian autosomal recessive trait and may be accompanied by hair loss, the so-called color dilution alopecia (CDA) or black hair follicular dysplasia (BHFD).
Gabor, M., Miluchova, M., Kasarda, R., Trakovicka, A., & Stanovsky, M. (2009). Genetic polymorphims of MLPH gene in Czech pointer breed.