|On this page
I discuss coat color. First, I cite the relevant section from
the standard. Next, I present a brief section on the genetics
of coat colour. It is not intended to be a complete description
of all genes/modifiers/promoters. Rather it is a practical introduction
and perhaps a reminder to breeders. Some excellent pictures of
dogs with different coat colours can be found on the Kombinalong
Australian National Kennel Council 1994 F.C.I. Standard No. 287
Blue - The colour should be blue, blue-mottled or blue speckled with
or without other markings. The permissible markings are black, blue or
tan markings on the head, evenly distributed for preference. The forelegs
tan midway up the legs and extending up the front to breast and throat,
with tan on jaws; the hindquarters tan on inside of hindlegs, and inside
of thighs, showing down the front of the stifles and broadening out to
the outside of the hindlegs from hock to toes. Tan undercoat is permissible
on the body providing it does not show through the blue outer coat. Black
markings on the body are not desirable.
Red Speckle - The colour should be of good even red speckle all over,
including the undercoat, (neither white nor cream), with or without darker
red markings on the head. Even head markings are desirable. Red markings
on the body are permissible but not desirable.
genetics of coat colour the Australian Cattle Dog
The most significant
genes in most Australian Cattle dogs are are agouti (A), spotting
(S) and ticking (T). Briefly, puppies are born
white and the coat converts to blue or red under the modifying gene
ticking. The patches are either black
or red depending
on which agouti (A) allele the dog carries. The spotting gene (S)
determines where spots occur on the body.
The cause of creeping
tan (where tan extends on to the thigh and shoulder) remains elusive.
Casual observation, suggests that creeping tan only occurs on plane
the genetic basis of coat colour is expected to contribute to the
debates concerning the replacement of "even read speckle" with "red,
red-mottled or red speckled" AND the replacement of "Red markings
on the body are permissible but not desirable" with "Red
markings on the body are not desirable."
A- Agouti series
The agouti gene is on chromosome 24. This gene undoubtedly has
several alleles, but how many is still an open question. Some
have been identified
using DNA studies and tests for agouti phenotypes in some breeds
will become available soon.
blue (probably very rare)
gene is dominant to at)
(blue with tan points)
(black saddle with tan on the rest of the body)
Most blue dogs
are at at (blue with tan points as shown by
the picture on this page) very few are AA. Most red dogs are ay ay.
As ay is dominant over at blue parents are expected to produce
blue pups. Homozygous red dogs are expected to produce red puppies.
reds ay at may produce red and blue pups. In other words, if
you mate 2 red dogs and get a blue pup then both parents must
for A. However, it is clear that there is incomplete dominance
ay and at. For example, ay at red dogs may have some dark hairs
in the red.
things, agouti has more than one promoter which seems to signal where
on the body, or even on individual hairs,
laid down. Roughly one seems to control ventral or belly
colour and the other dorsal or back colour. The simplest way to "see" this
is on a black and tan dog......the back is black from eumelanin
pigment being made and the belly is tan or red from phaeomelanin
being made. In some dogs banded hairs are produced over parts
of the body.
With certain genotypes, the coat color changes from birth
to adulthood, usually being born darker and then lightening. It is
possible that different promoters/ alleles of agouti is the cause
of "creeping tan" but
this is not known.
Berryere T.G, J. A. Kerns, G. S. Barsh, S. M. Schmutz. 2005.
Association of an Agouti allele with fawn or sable coat color
in domestic dogs.
This gene has at least four alleles or variants.
(white with large coloured patches on the head and body)
piebald spotting (white with large coloured patches possibly
to the head).
Some dogs who
are born white are also deaf. These white dogs are usually those
that are white from merle
crosses or from
the "Irish Spotting Pattern".
T – Ticking
Ticking is observed only in conjunction with the recessive alleles
of the spotting gene S. The ranges of variation from a light
speckle to a marked
that there are several modifiers operating.
pigmented spots in a light coat
Other genes of
b, has been documented and causes red/liver on the nose eyelieds.
E- Extension series
The recessive allele hides the effect
of black and results in a pale red or cream dog.
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