Color genetics

One of the important genes for the production of pigment is called the Melanocortin 1 receptor (Mc1r). Another name for the same gene is the Extension gene and in the literature the variants of the gene (alleles) are usually referred to as a capital E (dominant) or a small e (recessive). A third variant of the gene has been named Em and is associated with a so-called melanistic mask that occurs in Boxers and German Shepherds, among others. Em is a dominant trait and dogs with melanistic mask can therefore have both one and two copies of the Em allele. A genetic test for Em shows whether the dog carries one or two copies of the allele.

A Labrador or Flat Coated Retriever that has a capital E on both chromosomes (E/E) or one of the chromosomes (E/e) is black or brown. A yellow dog always has two variants of the small e (e/e) allele.

The black melanin, eumelanin can be “diluted” by another gene “Tyrosinase-Related Protein 1” (TYRP1) and give brown coat color. The yellow/red pigment, pheomelanin is not affected. The dominant wild type of the Tyrp1 gene in dogs is designated with a capital B and produces black coat color in Labrador and flat coated retrivers, among others, if the dog also has at least one capital E.

If the dog has two sets of the recessive small b allele instead, the coat color will be brown. There are at least three alleles of the recessive b allele (bS, bd, bc). In some dog breeds all alleles are present.