20/01/2020
Shared:
TYRP1-gene (Tyrosine related protein 1), this gene influences the production of brown or black eumelanin. This gene has been identified on the canine chromosome 11 (Schmutz et al 2002).
This gene has two alleles:
B - controls the black coat colour
b - controls the brown coat colour
Regarding brown coat color, three variant of TYRP1 gene were described: bs(c.991C>T), bc (c.121T>A), bd (c.1033_1035del).
Only in Australian Shepherd breed fourth variant c.555T> G was found.If two b-alleles are present, the brown eumelanin is produced.
The non-mutated allele or wild type allele causes the production of black eumelanin pigment and is dominantly inherited.
The presence of both genotypes EE and Ee at the same time allows the expression of the alleles of B-gene. The black B-allele is dominant to the brown recessive b-allele. The bb-homozygotes have brown nose and lighter eye pigmentation. Dogs with B-allele have a black nose, black lips and black pigmentation of mucous membrane. It is interesting to observe the occurrence of brown colour in hunting dogs, where it fulfils the function of camouflage during hunting.
Genotype variants:
BB - black coat colour
bb - brown coat colour
Bb - black coat colour (inheritance of brown coat colour)
The B-locus test is suitable for most dog breeds, especially for: Australian Shepherd Dog, Border Collie, Epagneul Breton, Cardigan welsh corgi, Shar Pei, American Cocker Spaniel, Curly Coated Retriever, Dachshund, Dalmatian, Dobermann, English Cocker Spaniel, English Setter, English Springer Spaniel, Field Spaniel, Flat Coated Retriever, German Short-haired Pointing Dog, German Wire-haired Pointing Dog, Italian Greyhound, Labrador Retriever, Large Munsterlander, Lowchen, Caniche Miniature, Newfoundland, Pointer, Pomeranian, Portuguese Water Dog, Poodlepointer, Toy Poodle, Bohemian wire-haired Pointing griffon...
The test is not suitable for french bulldogs. Their brown color is caused by different gene variant, that has not been identified yet.
Result interpretation
Test for locus B consists from three different tests - three markers called BC, BD, BS.
There can be three different results in each marker:
(note: small letter "b" means presumption for brown color, big letter "B" means no brown color)
possible results for BC: Bc/Bc, Bc/bc (carrier of bc marker - the dog has Bc from one parent and bc from the other parent), bc/bc (brown color - the dog has bs from both parents)
possible results for BD: Bd/Bd, Bd/bd (carrier of bd marker - the dog has Bd from one parent and bd from the other parent), bd/bd (brown color - the dog has bs from both parents)
possible results for BS: Bs/Bs, Bs/bs (carrier of bs marker - the dog has Bs from one parent and bs from the other parent), bs/bs (brown color - the dog has bs from both parents)
What does it mean "bc,bd,bs" result ?
There is a problem. Without the parents we are not able to decide which marker was inherited from which parent.
Generally, there can be two possibilities:
1) the dog inherited all small "b" together from one parent
parent1: bc,bd,bs - first gene allele includes all b
parent2: Bc,Bd,Bs - second gene allele includes all B
Final locus B expression would be B/b - the dog will be carrier of brown, brown color will be hidden
2) the dog inherited some small "b" from one parent and some small "b" from the other parent - for example:
parent1: Bc,bd,bs - first gene allele includes some b
parent2: bc,Bd,Bs - second gene allele includes also some b
Finall locus B expression would be b/b - the dog will be brown colored (brown nose and coat)
So if result is bc,bd,bs - we are not able to decide which marker is inherited from which parent. Locus B sumarry result cannot be in such case formed as B/b or b/b.
