Bicolor? - Page 5

1) the black&tan is a variant of the original wild type sable

Yes of course it it.  What  is incorrect in your first statement is that "black&tan and bicolor are each variants."  There is only one variant of A locus that accounts for all the tanpoint variations.

2) E locus does affect the A locus in their competition for expression.

Yes, this is correct too.  I don't think you have fully understood what I have said Daryl.  Please re-read.

a^s as a separate Agouti allele has been shown not to exist. And what is this as^m?  Are you suggsting Mask is on the A locus?  It has already been sequenced to MC1R.

This is the website of the lab at the forefront of colour DNA research -

http://homepage.usask.ca/~schmutz/agouti.html
http://homepage.usask.ca/~schmutz/mask.html

As Pod said, I believe that, what we refer to as a melanistic bi colour (showing minimal tan point) Especially when looking at the face the Em Mask gene is present and covering the tan points to the face, is it also affecting in some way or in conjunction with something else, the spread or breakthrough of pigment elsewhere i.e toe pencilling.

I'm in the middle of a discussion on an ACD forum about it, and not getting much chance to get online at the minute, but will reply better soon as I get chance.

OK, then perhaps I was misunderstood when I said black&tan and bicolor are each variants; what I meant was they are both variations on the same allele, the bicolor having greater loss of function than the other.

Somewhere between the saddleback pattern and the bicolor pattern falls the blanketback phenotype, and as^m was the notation I arbitrarily decided to use to indicate a broader area of melanistic coverage (blanket-backed) as recessive to as (saddle-backed).  My bad, this is the "made up" part, a theory based on what is implied by the forementioned findings.  If the mod hadn't deleted part of a previous thread, I wouldn't have such trouble filling the gaps between what I thought I already explained and where I'm leading with this idea.

Where we draw the line in the sand can almost be a subjective matter when we're discussing various levels of "lost function" on the same ancestral allele.  You might simply state the order of dominance is among three phenotypes of sable, blakc&tan, then black.  Most studies I've read have described it that way, the two extremes and everything else in between.

Or, you might get a little more complex in your breakdown and say the order of dominance is sable, saddlebacked, blanketbacked, bicolor, then black.  Even so, one could go further and more refined.  One single phenotype might not be necessarily identical to the same phenotype of a different family strain.

For example, some families of sables might carry a ventral stripe of black, while others do not.  That particular feature is confirmed as being linked to A-locus.  I would venture to guess that the ventral stripe is recessive, but other coding portions of the allele might hold greater importance for dominance in the order of things.

Just a little more info because I am in the process of doing genetic color testing on my "black" pup that now looks like a melanistic bi color....

http://www.vetgen.com/canine-coat-color.html 

The dog, if tested for coat color, has to be tested with the "k", "a", and "em". It is 3 different cheek swabs and takes 2-3 weeks to get the results back.

another topic that has been addressed before here - Genetically, black GSDs only carry black genes (two of them) and do not carry any other color gene including bicolor.  MANY if not MOST genetically black dogs will develop some "bleeding" or tan/grey hairs between toes, and sometimes extending up the legs as the dog ages.  I've seen some develop grey/tan hairs around the vent, too.  But despite the 'bleeding' the dog is still genetically black and can only pass on the black gene.  If your dog were melanistic bicolor in fact he would have been born with tan around the vent,even if the rest of the pup appeared solid black.

This is a black dog that developed bleeding as he aged.  His black sire did the same. 



molly

Here are two of my gsds (larger one with darker face is a two year old male; smaller one is a 6 month old female).  They aren't bicolor, but what would you classify them?


 


6 month old female (sitting)


2 year old male

Normal dark black/tan, blanket-back black/tan, black/tan.... not bicolor - nice looking dogs.

Somewhere between the saddleback pattern and the bicolor pattern falls the blanketback phenotype

Daryl even your comment indicates that you find that there is a distinct pattern for bicolor--such that there is a describable difference between "blanket back" and "bicolor".

I bred this female over her lifetime to a bicolor male that produced solid black puppies and 2 sable/black males--she never produced a solid black--she produced pattern sables, with and without toemarks--dogs her color, dark bicolors, and "light" bicolors. I describe her as a bt dog with bicolor recessive. It explains the patterns of her puppies pretty neatly.

It seems to make a strong argument for bicolor being a seperate, distinct pattern that is recessive to the typical saddle pattern--not just a different interplay of the masking gene.

Pod, are you saying that it's not a different pattern, just a modification, like the difference between a black sable and a dark sable? It's not the black recessive--so it's got be something like the masking gene, yeah? But in that case, it's not a different pattern, just intensity.

I've even observed some distinct differences when the dog is a sable:

sable with no toemarks (often with a saddle pattern): sable/b/t
sable with toemarks and clear "points": either sable/sable or sable/bi -- does not produce solid black
dark sable with toemarks: sable/black

Christine


Edit to add:
This site describes it, as well as the dominant and recessive black: bowlingsite.mcf.com/genetics/colorgen.html

Hmm. While looking at pictures for that post, I realized that the picture of Aly's mom has to be wrong--

www.pedigreedatabase.com/german_shepherd_dog/pedigree/17905.html

Eichenluft, my pup is 7 months old, has tan around the vent, tan between the toes, and is showing more tan around her legs. Her sire has the same, just less tan, but is registered as a black. His dam is a blanket black and tan but produces bi colors. This is why I am doing genetic testing on my pup. She looks straight up like a melanistic bi color.