The K locus plays a pivotal role in coat colour. This locus is a relative newcomer in our
understanding of canine colour, and includes traits formerly attributed by some
to other genes.
The dominant allele in the series is KB, which is responsible for self-colouring,
or solid coloured fur in pigmented areas. This trait was formerly attributed to
the Agouti (A) locus as AS, but recent breeding studies had shown
this not to be the case.
There are two other alleles, kbr, and ky. KB is
dominant to both kbr and ky,
while kbr is dominant only
to ky. kbr is
responsible for the brindle. The recessive allele, ky, allows the
basic patterns of the A locus to be expressed. So too does the kbr allele,
but with brindling of any tan, fawn, or tawny areas. Any animal with at least
one KB allele will be
Any animal with
at least one kbr allele,
and no KB alleles will be
brindled on agouti background (see A locus). Any animal with two ky alleles
will show agouti patterns (see A locus).
LABOKLIN can presently test for these two alleles. In some breeds, where no
brindle is present, this represents a complete analysis of the locus. An example
would be the Pug. In breeds where the breed standard disqualifies all but self-colored
dogs, testing for these two alleles is once again all that is needed. Any animal
with two KB alleles cannot
produce anything except self-coloured offspring. A prime example here is the
Labrador retriever. In breeds where many variations are allowed, these tests can
help predict the probability of potential litters to include fawn, sable, tawny,
tan point, tricolor or recessive black puppies.