genetics- strange litter colorwise........ - Page 5

Can you provide ANY factual examples of your theory of color genetics in GERMAN SHEPHERD DOGS????  If not, then why are you arguing about how much I know or don't know?  If you can't back up your theories with facts, then it's just theory.  My facts are proven to be fact.  In the accepted colors of GSDs (not getting into white masking genes) Sable is always dominant.  Black is always recessive.  Each dog carries two color genes, one of which is passed down to each puppy who receives one color gene from each parent.  The color of the puppy is determined by which inherited color gene is dominant.  It is, in fact, very simple.  Not complicated at all.  Anyone who knows anything about this breed knows this to be fact.  Not theory. 

I do love to learn new things.  But I prefer to learn facts, not guesses or theories not backed up with factual evidence.   I'd love to see your factual evidence of "dominant black" producing sable puppies when bred to a non-sable.  Can you provide this proof of your theory, or can't you?

molly

A sable pup CAN be the product of two black and tan parents (or any other combination of colors) IF both parents not being sable themselves carry a sable recessive gene. It's called a double recessive.

The problem with this statement is that in the GSD, the gene for sable is dominant to black and tan. You don't randomly get a dominant black and tan gene.

In most breeds, black is a dominant color but the dominant black gene was eliminated from the GSD many years ago. Recently, some showline dogs have shown up (in Russian bloodlines) who are solid black and who are producing solid black when bred to a black/red dog who has almost no chance of carrying the solid black recessive gene. If you look at the pedigree of these dogs, you can follow a single line of dominant black dogs back some generations. However, how did this dominant black get in there--possibly through a cross with some other dog breed that does still carry the dominant black gene (Belgian Sheepdog? Giant Schnauzer?). That said, this dominant black coloration is very rare--if this indeed what it is--and is found in only a few dogs. I have a few pedigrees bookmarked on my other computer, I'll look them up and paste them here later.

In the GSD, the dominance heirarchy is: 

[Dominant black] > sable(agouti) > black/tan pattern > black

A dominant black dog could carry the Dominant Black gene and a sable gene or a Dominant Black gene and a black/tan gene, or even, possibly, a Dominant Black gene + Recessive Black.

Otherwise, unless some odd color mutation is going on or an extremely rare color variation (e.g., a dog with a light undercoat like the smoke gene) causes a dog to be mislabeled as sable or b/t, there is no way that a sable dog could come from 2 black and tan dogs because in order for a dog to LOOK black and tan, it would not be able to have the sable gene. Black/tan cannot carry a recessive for sable--it doesn't work that way.

Christine

 Yes I can provide proof. I am not arguing sorry if it came off that way. I would appreciate if you would answer my questions. Are you educated in genetics at all? Where does your understanding come from? I'm asking so I have a sense of where to start, nothing more.

Dominant black does not exist in the German Shepherd Dog (as we know it).
http://jhered.oxfordjournals.org/cgi/content/abstract/75/4/247
--Mary

It *didn't* exist--but it may be back. Take a look at this pedigree:

www.pedigreedatabase.com/gsd/pedigree/623168.html

That is cool if it is a correct pedigree - unfortunately lots of pedigrees on the PDB are incorrect.  And, it is fact that there are black show-lines, so some black/reds do carry black recessive.  And, still doesn't show a sable produced by black X non-sable proving "dominant black" can carry a sable "recessive" gene.  It's all interesting though, I do like color genetics and would like to learn more about the "masking" genes and recessives such as where do blues, whites and livers come from?

molly

"[Dominant black] > sable(agouti) > black/tan pattern > black

A dominant black dog could carry the Dominant Black gene and a sable gene or a Dominant Black gene and a black/tan gene, or even, possibly, a Dominant Black gene + Recessive Black."



Christine, it has been known for some years that dominant black is not an A locus pattern.  The A locus goes in order of dominance from least eumelanin (dark) pigment  - A^y sable, to most eumelanin pigment - aa recessive black.  Black as top dominant in this series doesn't fit.

Dominant black has been assigned to the K locus and this has now been verified by DNA analysis.  This makes it epistatic to A locus pattern and dogs that are of this colour will carry two A locus alleles.  I believe we have had some threads on this forum giving  breeding results that suggest the presence of dom black because of additional A locus patterns showing up in litters, which would be impossible if the black parent were recessive black.

Very difficult to prove, as they all can be explained in other ways.  The only way is to DNA test.

I've not really studied the dominant black genetics, as until recently I didn't think it was relevant to GSDs. In my example above, I was talking mostly about phenotype. That is, if the dominant black gene is there, it will hide/prevent the expression of the other colors.

Pod, so a dog could be dominant black, on the K locus, and still carry, say, both a sable and a black and tan gene? So, the puppies from a dominant black dog could definitely turn out different colors if they didn't happen to get the dominant black gene.

Is the white gene also on a different locus?

Christine

Yep, that's all correct about dom black.  To produce A locus patterns, say sable and B&T, a dom black dog would need to be heterozygous a^w a^t   K k^y  All non dom black GSDs are k^y k^y

Yes, white is separate too.  It's the lowest recessive on the E locus.  Normal coloured GSDs (with mask) are E^m, those without mask are E and white is ee.  So a white carrier would be E^m e.

Blackthorn,the dog you gave a link to has for example this dog in his pedigree http://www.pedigreedatabase.com/gsd/pedigree/1120.html from maternal side, that explains the gene for black.