Brown

BROWN
*
b^b

This dog is genotypically a brown dog (base color), as evidenced by the color of
his nose leather, eye rims and lips and of course his glossy brown coat color.
He is also recessive k/k, because he is not masking the alleles from the Agouti
Locus. In order to know what he's carrying (color wise), or could possibly
produce, a person would need to know the color of his parents.

He is irish spotted and is a tan point pattern. This coloration would be called a
"tri". He is also non-white factored. You may have heard that a dog of his color
would be an excellent stud prospect to breed to a bitch of the merle pattern, this
is not always the case. Even though a dog of this color is minimally white, one
would still need to be selective because he could be carrying the color for extreme
pie bald -- and when bred to a merle, or one that is pie bald or carrying pie or
extreme pie bald, could produce offspring with too much white. This is why it's
very important to always know the color of the parents and grandparents. If
the lineage is not known, don't breed from that dog.

NOTE: This dog is from verifiable lineage; all parents and ancestors are known.

This gene, when in the homozygous recessive form, has a lightening effect on eumelanin (black-based
colors) only. It has no effect on phaeomelanin (red-based colors).

It is believed that the Brown Locus codes for an enzyme, tyrosinase-related protein 1 (TYRP1), which
catalyzes the final step in eumelanin production, changing the final intermediate brown pigment
(dihydroxyindole) to black pigment. SO, ALL dogs start as BROWN and after the final step --- this directs
the color to be black.

When brown (b/b) is expressed, it means that the final step in eumelanin production has not been
completed and the pigment remains brown. The brown color is not a genetic defect.

When the alleles are in the homozygous or heterozygous dominant form of B/B or B/b, the color and
pigment (nose, eye rims and lips) remains (or directs the color to be) black.

When the alleles are in the homozygous recessive form (b/b), the color and pigment will be brown. This
just means that the final step in eumelanin production of changing brown to black did not occur.
Phaemelanin (yellow/red [e/e]) is not affected. BUT, in the e/e colored dog, if the dog is also b/b; they will
be either red or yellow and will have brown pigment (nose, eye rims and lips). The pigment granules
produced by "bb" are smaller, rounder in shape, and appear lighter than pigment granules in "B" dogs.
The iris of the eye is also lightened.

Brown, ticked, with
irish spotting and tan
point pattern; called a
Brown-tri

Brown with tan point
pattern

Brown with irish spotting;
this female is dominant
K (meaning the agouti
alleles are being masked)