Genetics of Coat Color in Miniature Schnauzers
a summary of our DNA studies involving dogs of this breed
This webpage was mounted on July 13, 2013 and last updated on December 20, 2014 by Sheila Schmutz
There are only three coat colors/patterns in the Miniature Schnauzer according to the AKC and CKC breed standards: black, black-and-silver, salt-and-pepper. However, white is another color that occurs.
All 7 Miniature Schnauzers that we originally tested were aw/aw at the ASIP gene or A locus. C. C. Little (1957) had predicted that salt-and-pepper Miniature Schnauzers would be this genotype.
However, in 2014, we obtained additional samples and found that most dogs called black-and-silver had an at/at genotype. The plucking or clippering of coats in this breed apparently makes it difficult to identify the phenotype that is being caused by the ASIP genotype.
Miniature Schnauzers are black because they have a KB allele at the Beta-defensin 103 gene or K locus. They also all at least one E allele at the MC1R gene.
One would have assumed that ALL black-and-silver Miniature Schnauzers would be at/at, and most are. However, a few that are called black-and-silver have an aw/aw or aw/at genotype instead. Kona is a black-and-silver Miniature Schnauzer that DNA tested as at/at.
All are ky/ky at the K locus and have at least one E allele.
The legs are silver instead of tan because of some yet undiscovered gene that causes phaeomelanin (red, yellow, etc.) pigment to become pale and have no effect of eumelanin (black or brown) pigment. Hiruni Wijesena identified a variant in the SLC45A2 gene that is almost fixed in Miniature Schnauzers but rare in other breeds, except Scottish Terriers. We had hoped this variant was the cause of this paling of phaeomelanin in this breed, but there were a couple exceptions that made this unlikely.
Salt-and-pepper is another coat color variation. All dogs of this phenotype had an aw/aw genotype at ASIP and were ky/ky at DEFB103.
Black-and-silver and salt-and-pepper would be recessive to black because of the K locus. Salt-and-pepper would be dominant to black-and-silve because aw is dominant to at.
The gene causing white in Miniature Schnauzers is MC1R. All white dogs of this breeds have an e/e genotype. There are several other breeds, including German Shepherd Dogs where this same phenomenon occurs. In most breeds, dogs with an e/e genotype would be a shade of red or yellow. In a sense, white or cream, can be considered an extremely pale shade of red. Since all Miniature Schnauzers are fixed for the yet undiscovered gene that reduces their red/tan coloration to silver or salt, it is not surprising that dogs with e/e would appear white or cream.
Underlying the white, the dogs could be black, black-and-silver, or salt-and-pepper because the e/e genotype at MC1R is epistatic, or masks, both the A and K alleles. For example, the white dog in this photo is aw/at.
Dog Coat Color Genetics Main Page
HealthGene Dog Coat Color DNA Testing
Sheila M. Schmutz, Ph.D.
Department of Animal and Poultry Science
University of Saskatchewan
Saskatoon, Canada S7N 5A8
phone: (306)966-4153 fax: (306)966-4151