Falconara... (edited because I had GSDLuver in the attribute first, oops)
Love your post!
From what I have seen, I think that Panda's have an authentic completely new canine mutation that is not typical in most breeds based on the how prolific the Panda spotting pattern is, even when bred to solid dogs.
In most breeds a pinto bred to a homozygous solid (with no white at all) will almost always give you a dog that is almost nearly solid but maybe has a white chest medallion and a few white toes. But in Panda's it's so odd!
I think it's pretty cool. Thanks for your post.
I noted you didn't mention the 'w' that has been used so much to 'explain' white in the WS breed in the past. In a previous thread, I discounted the 'w' as well. It has not yet been found in dogs. It's probably still listed on WS sites.
I think rapid changes in molecular genetics have made it so that it's almost scary to attempt an 'up to date' article on canine color genetics.-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.
This material is invaluable in working in dog rescue because it does so much to help in breed identity of some cases.
GSDs and Anatolians have two common color phases. The black masked fawn dogs and a white version.
In my breed, when e/e (homozygous recessive 'white') dogs are bred together or e/e is bred to an E/e (a homozygous recessive is bred to a heterozygote for 'e'), we get typical punnett square probabilities of what some people call an akbash white. This homozygous e is hypostatic to anything in the A locus. I have however seen white Anatolians that with k-br and their black stripes do show up as washed out grey, so e is probably not completely hypostatic to k-br anyway.
Our breed genetics (Anatolian and GSD) are very similar as it regards the agouti signal peptide (A locus) and the recessive eumelanin 'e' (E locus). Of course, when two heterozygotes are bred together, there is a possibility of getting some whites in a litter. The AKC standard has its issues with white, but in the Anatolian we can certainly see this played out for generations.
Two alleles at the E locus? I don't know about GSDs but in the Anatolian, I think that Em is ubiquitous in my breed (when there is a dominant form of E at that locus). The white anatolians are homozygous e, so they never have a black mask. Thus I suspect in our breed genome, that there are only Em and e at the "E" locus -- with no plain 'E'. But we have yet to see as I don't know if any Anatolian color genetics has actually confirmed this behavior.
Do you know if GSDs have a plain E? Would you have a source or a paper? I think all colored GSD pups are born with some degree of mask, which may fade to just some darkness around the lips and ear tips, leaving them with black whiskers. So are they possibly only Em and e only as well?
I do however have questions about recessive 'e', since we do see black or gray hairs in the unweaned youngsters of some of these white Anatolian pups, yet the hairs become pale biscuit as the dog matures. Maybe some cases of 'e' are not so cut and dry.
Some of the coffee table books that show 'akbash' are actually showing a dog with dominant E. (the dog shown as an Akbash, most certainly is not)
Note Polo in this image that has been used in several breed books to illustrate 'akbash'. She has dominant 'E' because of her black whiskers.
I haven't seen a baby shot of her, but I believe she was born with a eumelanin mask that faded, later became quite yellowish over her whole coat, and as she matured, she ended up being a light all over reddish tan with a self mask, but still black whiskers. Here's a pic of her in her autumn years.
(this whole escapade of having her labeled as a 'different breed' was done at a time when people were trying to split the Turkish breeds into more arbitrary subdivisions that was not based on genetics)
WS are e/e so they will never have black whiskers otherwise, they would not breed 'pure' and could have black hair. The mystery is why white ASD and GSD can 'wipe out the black' with 'e' but also have their phaeomelanin 'wiped out' too. I wonder if there is some other hypostatic effect that e/e plays in the breed or some epistatic effect from another locus?
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