Mammals have two pigments that are the basis of hair color: eumelanin (black) and pheomelanin (red or yellow). The gene involved in the production of these pigments in many species including dogs is Melanocortin 1 Receptor (MC1R) which is also called Extension. Other genes modify these pigments to produce the variety of colors and patterns found in the domestic dog. The Brown gene, Tyrosinase-Related Protein 1 (TYRP1), is a modifier that dilutes black pigment to brown but does not affect red pigment. Other genes involved in canine coat color include Agouti (ASIP) which organizes the distribution of black and red pigments and Dilute (MLPH) which dilutes black to grey and red to fawn. There are other genes that add white patterns and other dilution genes specific to some breeds of dogs. Below are expanded descriptions of the genetic tests offered by the Veterinary Genetics Laboratory for dog coat color.
Test Results
Allow 5-10 business days for results.
Detailed Coat Color Information
Black/RedMC1R Gene. The three alleles (forms) of this gene are black (E), melanistic mask (Em) and red (e). E and Em are dominant to e, therefore a dog must have 2 copies of e to be red/yellow. Some breeds are fixed for either black or red, such as the Large Munsterlander for black and Irish Setters and Golden Retrievers for red. The melanistic mask allele restricts black pigment to the muzzle and face as seen in boxers and pugs. The Black/Red DNA test is useful for those breeds that have both black and red colored dogs such as Dobermans and Labrador Retrievers. The test does not detect the melanistic mask allele.
Black/Red results are reported as:
E/E: Black, cannot have red/yellow offspring.
E/e: Black, carrier of red/yellow.
e/e: Red/yellow.
Brown
TYRP1 Gene. There are two alleles: the dominant full color (B) and the recessive brown (b). Two copies of brown are needed to dilute black pigment to brown. For red or yellow dogs, the brown allele does not dilute the hair color, but will change the color of nose and foot pads from black to brown if two brown alleles are present.
Brown results are reported as:
E/E B/B: Black, cannot have red/yellow or brown offspring.
E/E B/b: Black, carrier of brown.
E/E b/b: Brown.
E/e B/B: Black, carrier of red/yellow, cannot have brown offspring.
E/e B/b: Black, carrier of red/yellow and brown.
E/e b/b: Brown, carrier of red/yellow.
e/e B/B: Red/yellow with black nose, cannot have brown offspring.
e/e B/b: Red/yellow with black nose, carrier of brown.
e/e b/b: Red/yellow with brown nose.
References:
Schmutz SM, TG Berryere and AD Goldfinch. TYRP1 and MC1r genotypes and their effects on coat color in dogs. Mammalian Genome 13:380-387 (2002)
Schmutz SM, TG Berryere, NM Ellinwood, JA Kerns and GS Barsh. MC1R studies in dogs with melanistic mask or brindle patterns. Journal of Heredity 94:69-73 (2003)
Newton JM, AL Wilkie, L He et al. Melanocortin 1 receptor variation in the domestic dog. Mammalian Genome 11:24-30 (2000)
Dilute
A recessive mutation in the melanophilin (MLPH) gene was identified as the cause of color dilution phenotypes in the dog. Two alleles (variants) are described: the dominant full color (D) and the recessive dilute (d). Two copies of dilute are needed to lighten black pigment to grey (often called blue) and red pigment to cream (also called buff). A diagnostic DNA test identifies the specific variants of the MLPH gene.
Results from the DILUTE test are reported as:
D/D Full color, no dilute gene present
D/d Full color, carries 1 copy of the dilute gene
d/d Dilute, 2 copies of the dilute gene
Reference:
Drögemüller C, U. Philipp, B. Haase, A-R Günzel-Apel & T Leeb. A noncoding melanophilin gene (MLPH) SNP at the splice donor of exon 1 represents a candidate causal mutation for coat color dilution in dogs. Journal of Heredity 98(5):468-473 (2007).