coloration is controlled by several different genes in dogs. One
of these gene is referred to as "Dominant Black." The
presence or absence of this gene determines if a dog can express
"agouti" color patterns.
The Dominant Black gene consists of three different
alleles, or variants. The first allele, which is dominant, is noted
as "KB," or dominant black. The Dominant Black allele
is actually a mutation that does not allow the agouti gene to be
expressed. Because this mutation is dominant, a dog only needs to
have one copy of the mutation to suppress the agouti locus. A dog
that has one or two copies of the Dominant Black allele will only
express his base coat color, which is determined by the B-Locus
and E-Locus. He will not express any colors that occur from the
agouti gene, such as "black and tan" or "tricolor."
The second allele is known as the "brindling"
allele, and is represented as "Kbr." The Kbr allele is
a separate mutation that still allows the agouti gene to be expressed,
however, causes brindling of the agouti patterns. The agouti gene
represents several different colors, such as fawn/sable, tricolor,
tan points, or recessive black.The Kbr allele is recessive to the
KB allele, however, it is dominant over a third allele, Ky. Thus,
for a dog to express the brindle pattern, he must be either Kbr/Kbr
or Kbr/Ky. Dogs that are KB/Kbr will not appear brindle, but can
still pass on that allele and potentially produce brindle offspring.
The third allele is represented as "Ky."
This allele allows the agouti gene to be expressed without brindling.
When a dog is Ky/Ky at the K-locus, the agouti locus determines
the dog's coat color. For example, a dog that is Ay/Ay at the agouti
locus could be fawn/sable. If that same dog is KB/KB at the K-locus,
the agouti locus will be hidden, and his coloration will be determined
at the B- and E- loci. However, if that same dog is Ky/Ky at the
K-locus, he will then be able to express agouti, and will be fawn/sable.
At this time, there is no direct test for
the "Kbr" allele, although it can generally be inferred
through testing for the presence of the Dominant Black allele, as
well as through phenotypes of the parents and offspring. Testing
for the Dominant Black mutation determines if the dog is able to
express agouti phenotypes, however, it is limited in that it will
not tell you if the dog will be brindled.
Genetics currently offers a test for the K-Locus to determine how
many copies of the dominant "KB" allele a dog carries.
US for the KB-allele test.
sample using buccal swabs provided by Animal Genetics. Ensure that
the dog has not eaten within a few hours of sample collection. Any
food particles can inhibit the test. Rub each of the swabs along
the inside of the dog's mouth for 10-15 seconds, and allow the swabs
to dry thoroughly. Label the provided envelope with the dog's name,
and place the swab inside it. Download and complete a submission
form for each sample and send along with payment to Animal Genetics
Results are given using
the following symbolic notation:
dog carries two copies of the dominant "KB" allele.
The dog will be not be brindled or express his agouti phenotype.
The dog will always pass on a copy of the "KB" allele
to all offspring.
copy of the dominant black allele was detected. The dog will
be dominant black, and will not express his agouti phenotype.
The dog could pass on this allele, or either the brindle or
fawn allele, to any offspring.
|The dog does
not carry the dominant black mutation. The dog's coat color
will be determined by the agouti gene, and may be brindled or