Coat Colour Genetics - in the dog
The study of coat colour in dogs has interested breeders for many years, yet the inheritance of the many colour variations is often poorly understood. Terminology has been (& often remains) a complicating factor in our understanding of coat variations, while the identification and characterisation of both coat colour and texture has also slowed progress in this field.
Much of the earlier work on coat genetics was published in now hard - to - obtain books, but recent progress has been well documented.
Coat colour in dogs depends on the melanins (pigment) present, both in the skin and in the hair. Melanins may occur in two forms: Eumelanin (Black derivative including chocolate brown) or Phaeomelanin (reddish brown or yellowish). These two forms of melanin act differently genetically, but it may be difficult to distinguish visually between very dark phaeomelanin and light eumelanin. The combination of alleles interact to produce the final coat and the absence / variation in levels of pigment in the coat may occur across the whole coat or in specific areas.
The wild type of coat is considered as the standard coat colour / texture. This adds to the confusion involving coat colour as the colour of Wolves (Wild Type for dogs) includes many phenotypes ranging from dark black - pale sable - silver. White (as a distinct colour) occurs either by the dilution of pigment, or by the absence of melanin in specific areas (aka white spotting). Below follows some brief explanations of terms and please view my other coat colour pages for further information.
A brief summary of common definitions:
| Gene | Functional unit of heredity - the entity by which characteristics are passed through generations. Offspring are created using half the genetic information present in each parent (i.e. offspring will contain two alleles of each gene - one from each parent), and may therefore be homozygous or heterozygous at that position. |
| Genotype | The genetic composition - all genetic information in one dog. |
| Phenotype | The visual composition - all observible characteristics in one dog |
| Chromosome | Strands of genetic material where genes are located. |
| Locus | Specific position of a gene on a chromosome |
| Allele | Any form / variation of a gene occuring at a specific locus |
| Wild Type | Natural phenotype, characteristic of most members of the species |
| Mutant | Any change from the 'normal' / Wild Type |
| Homozygous | Where both alleles of a gene are identical |
| Heterozygous | Where both alleles of a gene are different |
| Dominant gene | Produces the same phenotype whether present as homo- or heterozygous state |
| Recessive gene | Only produces phenotype when present as homozygous state |
| Autosomal | Any chromosome with the exception of the XY sex chromosomes |