The B Locus in Dogs
This webpage is part of a series on Dog Coat Color Genetics and was last updated on October 10, 2010 by Sheila Schmutz
The gene at the B locus in dogs is Tyrosinase Related Protein 1 (TYRP1). This same gene causes brown in several other species, such as mice, cattle and cats. Brown is a type of eumelanin pigment.
The two dogs at the left are representatives of the two possible color phases of the Large Munsterlander. Most Large Munsterlanders are black and white but occasionally a brown and white one is born. All Small Munsterlanders are brown and white.
The reason that the German Longhair, who is E/E, is always brown or brown and white and the Large Munsterlander, who is also E/E is usually black and white, is due to TYRP1. The black allele B is dominant to the brown alleles (bS,bd, bc). There are actually 3 common mutations (bS,bd, bc) and perhaps additional rare ones that occur in this gene which result in brown instead of black eumelanin production. The alleles were named based on the type of mutation involved. Most of the DNA testing companies simply report all the alleles as b.
The nose leather, pads, and eye rims are also affected by this gene. They are black if a B allele is present but brown if not. Hence all brown dogs have a brown nose and all black dogs have a black nose but red, fawn, sable, white, etc. dogs could have either black or brown noses.
In dogs which are yellow to red (e/e at MC1r), TYRP1 mutations affect the nose and pad coloration, changing it from black to brown. Yellow lab puppies can have black or brown noses, but Vizslas always have brown or flesh colored noses.
All dogs which have brown coat color have at least one E or Em allele so that eumelanin is produced. The German Longhair, above, is homozygous for one of the common mutations. Her genotype is bdbd. The brown Large Munsterlander, above, is homozygous for the other with a genotype of bsbs. The Newfoundland, at the right, is homozygous for the rarer brown mutation. His genotype is E/E, bc/bc. Dogs which have any of these mutations on both chromosomes would also be brown, i.e. bs/bd.
Although Sabastian, the Newfoundland appears to be a darker shade of brown than the other two dogs, we do not think that it is due to which b alleles he has. We have studied a litter of Cheasapeake Bay Retrievers (whelped by Macy below) who had different shades of brown, but all had the same genotype of b alleles.
Smaller breeds such as the American Cocker Spaniel can also be brown.
In some breeds, such as Doberman Pinschers and Australian Shepherd the brown dogs are called red. See the chart below for the various terms used for brown by various breeds. The miniature Aussie at the right, is brown-and-tan.
The typical Weimaraner is also brown, but a dilute brown. See more about dilute due to MLPH mutations on another page.
Breeds in which brown dogs of with TYRP1 DNA changes have been detected
The list of alleles may not be complete because relatively few dogs have been tested for some breeds
|Breed||Term for Brown||Alleles Present|
|Australian Shepherd||red||bs, bd|
|Border Colllie||Brown||bs, bd, bc|
|Chesapeake Bay Retriever||Brown, Sedge, Deadgrass||bs, bc|
|Chinese Shar-Pei||Chocolate, Lilac||bs, bc|
|Cocker Spaniel||Brown, Liver||bs, bd, bc|
|Dalmatian||Liver||bs, bd, bc|
|English Setter||Liver Belton||bs|
|English Springer Spaniel||Liver||bs, bd|
|English Pointer||Liver||bs, bd|
|Field Spaniel||Liver||bs, bd, bc|
|Flatcoated Retriever||Liver||bs, bd|
|French Brittany Spaniel||Liver||bs, bd|
|German Shorthaired Pointer||Liver||bs, bd, bc|
|German Longhaired Pointer||Liver||bs, bd, bc|
|German Wirehaired Pointer||Liver||bs, bd, bc|
|Italian Greyhound||Isabella, Chocolate||bc|
|Labrador Retriever||Chocolate||bs, bd, bc|
|Large Munsterlander||Brown||bs, bd, bc|
|Newfoundland||Brown||bs, bd, bc|
|Poodle||Brown, Cafe-au-lait||bs, bd, bc|
|Portuguese Water Dog||Brown||bs, bd|
|Pudelpointer||Liver||bs, bd, bc|
|Small Munsterlander||Brown||bs, bc|
|Weimaraner||Mouse-gray||bs, bd, bc|
It is interesting to note that brown is common in bird dogs but not too common in other breeds. More than one of the brown mutations were found in the short-haired breeds: Labrador Retriever, German Shorthair, Vizsla, in the wire-haired breeds: German Wirehair, Pudelpointer, Griffon and in the long-haired breeds: German Longhair, Large Munsterlander, Small Munsterlander, Field Spaniel. Many historical records of hunting dog breeds suggest that the hair types were differentiated about 1100, even though the breeds may not have separated for almost another 100 years. Therefore it would seem that these mutations may have occurred before 1100, but certainly before 1850. Brown was probably selected by breeders for its camouflage appearance in hunting breeds and therefore proliferated there.
The painting entitled "Meeting of the Gun Dogs Society" at the left is a portion of one painted by George Earl in 1904 and illustrates that black, brown, and red dogs all occurred by then. I thank Gabriel Palacio of Spain for correctly identifiying this painting.
Furthermore Gabriel Palacio has found a painting by Pisanello "The Vision of St. Eustace" held by the National Gallery in London which they estimate was painted about 1440. This painting shows three dogs at the feet of the horse. A spaniel type dog behind the front leg is brown-and-tan. This is seen better if you click on "image only".
In a few breeds some dogs are called "brown" or "liver" or "chocolate" and they are not a typical brown color. Such an atypical case is called "seal" in some breeds. The genes responsible for seal are yet unknown but such seal dogs would test B/B, and also have a KB allele and at least one E allele.
I have also seen a few brindle dogs that look brown in some photos but are actually typical brindles with black and some shade of phaeomelanin striping interspersed. Again such dogs would not test as brown (i.e. b/b).
In Chinese Shar-Pei there are true brown dogs that are called chocolate and there are also dogs called brown which are not "true brown". These dogs have intermingled phaeomelanin and eumelanin hairs and have a black nose and pads.