gsd colors - Page 5

Pod -- "Very interesting Christine.  As I've said I don't have that much knowledge of the breeding data in GSDs and it's great to see your ideas.  Must say I'm surprised to see that saddle can carry rec black.  Have you known of this in more than one dog?"

Yes, but it's pretty unusual. One was the Pike daughter Cira v Conneforde, who was a saddleback black and tan.

With your newest proposal, is it possible for a black sable parent and a bicolor parent to produce black and tan offspring?

a^wa mm^h = sable, black recessive, very dark sable
a^wa m^hm^h = "black" sable

a^ta^t m^hm^h = "bright" bicolor
a^ta m^hm^h = dark bicolor

Let's take the darkest possible combination....

a^wa m^hm^h
a^ta m^hm^h

aw/at mh mh
aw/a
at/a
a/a

All pups will be homozygous for heavy pigmentation, so you'll get sable/black (dark/black sable), sable/bt (the dark pattern sable color of Elkoor's dog), bt/black (with double melanization modifier, this would be a dark bicolor), and solid black.

Now if one of the parents is not homozygous for heavy melanization, you'll get a bit more variation.

What do you think, Daryl--does this support or contradict actual experience?

Christine

I think that you cannot get a black and tan from a sable parent (with black recessive) and bicolor parent. Black and tan cannot arise from a bicolor. I believe that's what you're suggesting, when you think that bicolor is controlled from a different locus.

But saddle pattern (not even blanket back) isn't one of the options if you assume that both parents are homozygous for the heavy melanization modifier--so it looks like the modifier option hasn't been contraindicated yet.

All pups will be homozygous for heavy pigmentation, so you'll get sable/black (dark/black sable), sable/bt (the dark pattern sable color of Elkoor's dog), bt/black (with double melanization modifier, this would be a dark bicolor), and solid black.

The options I describe are, phenotypically, black sable, pattern (black) sable, dark bicolor, and black. 

Do you have a picture of her, VonSisk?

It's unusual for a dog with a saddle pattern to have the black recessive--usually the dog will be a blanket back if it is a black-tan pattern with the black recessive.

I think, however, that there are some other elements at play in addition to the proposed melanization modifier. I think there is probably another heavy pigment factor at play---what makes some bicolors with the black recessive have clear tan areas and others are very muddy looking?

What makes some bicolors appear solid black? Are some blacks with bleedthrough really bicolor dogs with extra heavy pigmentation? What, genetically, is the difference between a very dark sable (carrying the black recessive) and a really black-looking "black sable"?

There's a thread on the GSD section right now about 2 apparently black parents who had bicolor puppies--obviously there's something at work there that doesn't fit our current knowledge of GSD genetics.

We've had previous threads here that suggest dominant black may be present in the breed, possibly from outcrossing to another breed or even a point mutatiuon.  This could explain the appearance of other A locus patterns from black x black breeding.  An unbroken line of solid colours (Black, liver, white) in the pedigree could indicate how far back the mutation or outcross was.

BlackthornGSD,

IMO the second picture you posted could be Black & tan with either black or bicolor recessive gene, how positive are you it is bi color?

Ibrahim

IMO the second picture you posted could be Black & tan with either black or bicolor recessive gene, how positive are you it is bi color?

Ibrahim

I'm not at all positive. I could indeed be wrong--but look how clear and distinctive the tan areas are. But her dad is a dark bicolor and so is her brother. If you click on the picture, it will take you to her PDB pedigree page.

And she doesn't look at all like what I've witnessed of dogs who would be described as black-tan/bicolor (see my pictures of Nike). And a black-tan with black recessive doesn't usually have the distinct pattern areas of tan (see the pictures of Xita).