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RE: [pyrnet] Black Pyrenees, White Newf...
Hi
Joe, Barb and Linda,
This
is an extremely interesting thread. I am of course no expert in dog coat
colorations, but I have done some research in Horses. I was wondering if some of
the same genetics as far as colour genes may be similar. Please excuse my
intrusion and ramblings as I'm thinking out loud here.
Horses
I'm sure you know is an animal where extensive study has been done on the
subject, as people strive to guarantee certain colour and coat patterns...i.e.:
Paints, Appaloosas, Palomino's etc. Although they do not always get the desired
results :(
As in
horses, true white horses (albino) are very rare. Most white horses are actually
grey horses which have faded to white. The same is true for black horses. A
black horse is also extremely rare (except in the case of breeds like the
Friesian who breed for it) most black horses are actually a very dark
brown.
Linda's extreme piebald theory seems like a very good explanation, as
I've never read the book she mentions and it may explain further detail and
suggest a similar explanation..... I would also suggest for discussion, that
maybe they also have the dominate "greying" gene or a "dilution" gene as well.
Which
might explain why alot are born with color, and it fades as they age. Firm rule
in horse breeding, you never breed a Grey horse to a Paint if you want the
coloration to stay. Or a Palomino (dilution gene) to a Paint for the same
reason.
In the
case of the dilution gene, if is homozygous, it will result in any
colour becoming diluted to a very pale cream or white.
Appaloosa breeders steer away from the dilution factor as it lightens the
dark pigment, so there is little or no contrast between the white and the colour
in the horses coat.
According to Ann Bowling, PHD at the Veterinary Genetics laboratory at UC
Davis; "Despite the great variety in coat colours, they're all created by the
presence or absence of two pigments, eumelanin (black/brown) and phaeomelanin
(red/yellow). It's believed that these two pigments may be influenced by other
genes that can alter the coat colour, diluting it or producing
patterns."
So in theory, maybe Pyr's are actually not white but have the colour
gene's (red/yellow) or (black/brow) pigment in a Overo coat
pattern and the dilution gene, which makes their coat fade to either white
or white with pale colouration. Or the combination of the greying gene with the
piebald.
Again
just thinking out loud.
Sariena
In a
message dated 7/8/02 8:17:31 AM Eastern Daylight Time, lmweisser@attbi.com
writes:
. Pyrs are identified as extreme piebald in Little's book
The
Inheritance of Coat Color In Dogs which is, decades later, still
considered
the "bible" of color inheritance. Now, there has been
some debate over the
identification of Pyrs with this inheritance
pattern. That is a legitimate
debate but no "better" explanation
has been put forward.
Here is part of a web site by
the
Department of Animal and Poultry Science
University of
Saskatchewan
Saskatoon, Canada S7N 5A8
Some pure white
animals are albinos. Little discussed albinism in dogs but this condition is
probably rare. This white Samoyed/Husky cross has a black nose and eyes and is
therefore not an albino. Little suggests that the white of Samoyeds is due to
the allele (sw), which he claims is the lowest allele of the series at
spotting, meaning it is the most recessive in that series. However, this
crossbred suggests that Samoyed white is dominant. No data are yet available
for which gene actually causes this white or the white of Great Pyrenees.
This site is purported to be a summery of the accepted publications on
the Color in Dogs and used Little's work as its main template.
The
subject is not definitive at all and we should look carefully at it.
Joe