Color Genes for GSD's - Page 4

Yes Daryl very similar;  the one I saw most of was a coat, so the
markings were more noticeable as she got older.  Interesting that
neither parent in yr e.g. were maximum 'dark';  Hutch pretty heavily
pigmented, Nyx less so.  ?? Going by their photos anyway as
that's all I've got to look at.

Thanks Daryl for sharing, very interesting, one thing more I miss your posts, wish you post more frequent

She was pretty gray at the time of that pic, and the sunlight glare made her appear even lighter.  In the pic below, Hutch is shedding but it shows Nyx's normal color more accurately.



So then, with these two dogs who have clearly demonstrated that each carries a recessive black, by having had completely black offspring, I can guess that one of two things must be occuring.  1. The bicolor markings are somehow inherited from a loci other than the agouti allele, and when present, over-ride the black expression.  Or 2. Reverse mutation has caused a gain-of-function mutation (GOF) acting on a black allele at the agouti loci, negating a portion of the codons that block the expression of the wild-type original allele.  (Black alleles, essentially being sable alleles with a early section of codons that fully turn off the sable expression for the entire allele.) 

As a sidenote, Hutch has had other solid black offspring with other females, with no changes.  And in Nyx's pedigree, I'm not certain that Eli Va-Pe doesn't have some tan markings himself, other than the solid black that he appears to be at first glance.

And Nyx looks considerably darker in that picture
than she does in her pedigree page photo.
Thanks for sharing that - did you take it yourself ?

Really not advanced enough in genetics to know
whether your '1' or '2' might be right;  interesting, food
for thought.  There is still clearly much to confirm,
despite how far science has advanced in these
areas.

Well, "pod" is well versed in genetics, and she has argued against option 2's possibility at all, insisting that black or black/tan alleles are totally different than sable.  I believe the other allelic types to be mutated versions of sable (wolf-gray).  This would also support why certain strains of one allelic type are sometimes slightly different from other strains, but phenotypically consistent in expression through their own line of descendancy.

I myself on previous occasion argued against the possibility of option 1, having seen no previous examples on record of bicolor even possibly occurring outside the agouti locus, that the number of phenotypic results hadn't supported the possibility.  Given this example, that possibility is present.  The fact that it occurred in my own breeding a year ago makes me wonder why I could find no pre-hand evidence in my bloodline research or other people's experiences.

I know of at least one case where someone did the DNA testing for color on their bleed-through black dog--and it tests as recessive black, and based on other experiences, it breeds true as recessive black.

So I think the bleedthrough blacks must have some modifier to cause the color change.

I have shared that line of thought myself, but are you of the opinion that the example I posted above is "bleed through" on black?   Could be a modifier whatever it is, but I thought it appeared to be more than "bleed-through" examples I've seen others post before.  I've had lots of black dogs, but never with bleed through.  Unless you would count my son of Cak who had tan between the toes, which you had to spread wide to see it at all.

Yes, I still consider that a bleed-through black--just a lot more color than sometimes is seen. That's about the amount on the pictures of the dog that I know of that was DNA tested (ugh, tortured sentence structure!).

Christine
 

Informative discussion

Earlier this year my black/red male was bred to an all black female.  Out of 11 pups, 5 were black, one or two with small white chest blazes.  There is no possibility of an "Oops" breeding to any other male.  The black/red male DNA tested for recessive black.  He does not carry it.  Some friends in Germany suggested that it was possible for the female to be dominant black.  Her pedigree is a mix of old Czech working blood, German high lines and American off shoots.  I kept back a lovely black female, now almost 9 months old.  Will eventually test the young female for her DNA coat make-up.  So far she is all black with a few individual gray hairs in her armpit area.   I can't find any info on dominant black in GSDs.  Anyone have some insight?

Gayle