Hello all - some of you know me as Ceph - but that account I asked to have locked and I thought I would start over with a new handle....there have been alot of new things since I was here last, but mostly I have been playing with my new puppy Ruby and learning alot about Genetics.
I thought I would share some of the research I have done on the coat color genetics of the GSD - you have to keep in mind that genetics are not set in stone and that some of this has changed...but most of the research I did was based of studies done by geneticists who are published in the J.Heredity, have written books, or Dr. Willis (a well known geneticist in the GSD world) and Dr. Sponenburg (one of the worlds foremost color geneticists...lol, the horse peeps could probably back me up on this) I have posted this elsewhere before, but I made some updates since some things have changed : for example - there is a strong possibility that the Chinchilla affect or the Cd dont cause the white coat and it is instead caused at the extension locus, however I kept the information there and updated the extension section because the Color locus was a very widley accepted possibility for a while.
Anyway : here it is...I hope ya'll like - and also - most of this applies to other dogs as well...I didnt list a bunch of Loci because they dont affect the GSD persee because they are homozygous in those Loci. I listed three examples at the end....if ya'll have any questions about coloring though, I would be happy to answer them
My Sources :
A. Ruvinski and J. Sampson the Genetics of the Dog (Ruvinski and Sponenberg)
Willis, Malcom B. The German Shepherd Dog : A Genetic History
White shepherd Genetics Project : wsgenetics.org
Standard Acceptance of Coat Color in Dogs : www.chromadane.com/standardcoat.htm
Genetics of Coat Color and Type in Dogs : homepage.usask.ca/~schmutz/dogcolors.html
Coat color in the GSD
The Agouti Locus – controls coat pattern
A – dominant or self black (some geneticists feel that this should be removed to its own Locus – it is not present in the GSD
ay – Tan or Gold Sable (can be ay-ay; ay-aw; ay-as; ay-at; ay-a)
aw – Grey or silver sable (aw-aw; aw-as; aw-at; aw-a) (this is often called wolf color, and may have banding within it)
as – Saddle marked (as-as; as-at; as-a)
at – bi color (at-at; at-a) (color goes further down the legs)
a – No pattern (a-a)
The Black Locus – controls black pigment formation
B – Allows Black pigment to form
b – blocks black pigment in favor of brown, choclate, or liver
Notes on ‘b’ :
-affects both skin and coat simulaneously, and also may be linked to eye color because livers have lighter eyes.
-early views that liver may be lethal were discarded as improbable, and there is no real evidence that it is biologically harmful (Willis, pp39)
The Color Locus – controls pigment in the fur
C – wild type (no change, and no dilution)
cch – Chinchilla affect – partial albinism ‘washy’ coat color (dilutes tan to a yellowish cream or white)
cd – pure white coat with black skin pigment in nose, eye and pad leather.
ce – cream colored coats, extreme dilution (from chromadane)
cb – carnaz coats and blue eyes (from chromadane)
ca – true albino (interuption of tyrosene pathway) (from chromadane)
Notes on cch/cd/ca
-for ca there is still a fair amount of research being done
-in Willis’ book he states that cd is an iffy in the GSD – many believe that homozygous cch is the cause of the white coat in the GSD
-the long held belief that white is degenerative or linked to biological problems is w/o foundation (Willis, pp39)
-seriously defective hips are not a feature of or pecuiliar to whites (Willis pp39)
-on this I think he mentioned that whites have a smaller gene pool because they are ****-r, however, with careful breeding and testing they are not any more prone to hereditary disease than are any other GSD (the swiss have demonstrated this with their superior breeding of the BBS)
-whites were generally chosen against in the past because it made it difficult to herd the white sheep and to blend into the dark when guarding. However, Willis states that the White GSD could be very useful as guide dogs if trained properly and he also mentions that they have no diminished desire to herd.. I feel they would almost be more useful during SAR missions because they would be easier to see.
-whiwhite dogs are controverisial with some breeders because the white color is correlated with skin, eye and ear defects. A few studdies have failed to demonstrate that relationship, but even so, white dogs in these breeds remain unpopular (Ruvinski and Sampson, pp82)
The Dilution Locus – dilutes black pigment
D – causes dense black pigment (also known as the wild type)
D – dilutes black to blue or silver
Notes on blue dogs :
-like liver the blue affects the skin and coat simultaneously, as well as having lighter eyes
-blues used to be shown in confirmation until a blue won a championship, at which point they were disqualified (willis, pp40)
-BBdd looks almost like a black dog dipped in flour – the blue causes a dusty sheen and can be mistaken as a sable
-the blue color may disapear with age though usually some blue pigment will remain on the muzzle
-Some puppies are born ‘silver’ which is a sable color that appears to be blue. However as these puppies age the normal black pigment develops (Willis).
The Extension Locus restricts the location of the dark pigment
Em – Black or dark mask
E – dark coat but no black mask except in black dogs
e – clear tan (black usually fades…restricts pigment to red or yellow)
Notes :
-the ‘e’ is more apparent in dogs with tan coloring than in grey sables.
-according to schmutz the e-e has been mapped to the MC1R gene and is now known to be linked to the white coat color of White Shepherd Dogs.
The Intensity Locus – dilutes tan colors
Int – dilutes tan to ditry white
intm – dilutes tan to light yellow
int – no dilution (wild type)
-Notes :
-The intensity locus is what controls the color of the GSD as far as the tan goes. The tan can range anywhere from a very deep red (int-int) to a silver or cream color (Int-)
-The majority of the really red dogs carry the recessive gene which is being selected for and bred for.
The K Locus – causes self black, originally thought to be part of the Agouti Locus
K = Dominant or self Black
Kbr – sepculative causing of brindle coloring
k – speculative recessive allele, or wild type
Notes
-this whole locus is considered very new, so there may still be information out on it.
-most GSDs would be k-k; however there have been very rare cases of brindling in GSDs : CH Donna V Allergeiligentor (b. 1924) and her son Igor of Ceara (b. 1927) were both GSDs and brindle, so there may be a few dogs still carrying that allele, though very, very few. They may have also been the progenitors of the Dutch Shepherd Breed.
The S Locus – allows for white spotting
S – self colored dogs
si – Irish spotting – 10-30% white (feet, lower legs, belly, chest, tail tip, color and blaze)
sp – Piebald – 20-30%white
sw – extreme white piebald – 10% or less is pigmented
Notes :
-S is incompletley dominant w/ sp – it causes irish type spotting, (psuedo Irish)…Can produce white like beagles have
-S-sw or si-sw makes the dog sp-sp looking.
-I included this Loci because I believe it is what causes Panda spotting in the GSD…I don’t know for sure because there are no recent GSD genetics books that I could find, but it seems like a possibility…It is also in all liklihood fairly rare in the GSD to have the spotting, though clearly exhists as is demonstrated byt the Pandas (dont quote me on this one ...I am not a geneticist...I am just guessing)
-The S locus is probably in all liklihood what controls those small spots that may occasionally appear in the white coat of the shepherd.
Some other nifty info is Coat length :
L - Short Coat
l - long coat (recessive)
All GSDs are thought to be m-m (non merle); g-g (non grey); and t-t (non-ticked)
I hope some of this was informative
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-because when you wake up in the morning after writing something that is 'up to date', yet another thing is found that increases the confusion of all but the most loyal of enthusiasts in the path of understanding coat color genetics. I'm a fan of Chromadane's site and Schmutz's and read them often.
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