Colour inheritance: black sable - Page 1

I've mentioned on here before, the proposed theory that the black sable phenotype is formed by the Agouti locus heterozygote genotype a^w a (sable carrying recessive black).  I've been looking through the database and from what I can find with my very limited knowledge of bloodlines, is that breeding results tend to support this.  But what puzzles me is why this colour seems to be confined to DDR lines.... or is it?  If it is, this tends to support the usual belief that the extra black pigment is the product of modifying genes.

I know both sables of any type, and blacks are not exactly popular in the modern day showring but surely we should have encountered some black sables over the  years if this theory were correct.  Are there any instances of them in pure show lines?

Also, does anyone know of any instances that would not support the theory eg tanpoint (any type of black & tan/ red/ gold - bicolour, saddle) pups from a black sable x black sable mating.  The expected ration from this mating would be 2:1:1 - black sable:sable:black.

Or a black sable x black mating producing tanpoint or regular sable pups.  Expected ratio 1:1  - black sable:black.

Or a regular sable producing black offspring.  That should also not be possible if the presence of recessive a in a sable always expresses as a black sable phenotype........ or does it? Maybe additional modifiers have to be present too and these are exclusive to the DDR lines.  Any thoughts?

I use the term "dark" sable when referring to the phenotype, and "black" sable when I have confirmed presence of a black recessive.  I've seen a few very dark sables that did not carry the black recessive.

Confined to DDR lines?  I've seen a few exceptions, though not many, and believe that due to the influence of selective breeding for the black & tan phenotype and the linebred overiding influence of showlines.  The presence of black through a long line of black & tans could suddenly appear due to a bicolor dog far back in the pedigree.  It's generally the sable that is being selected against in these bloodlines, and the black is difficult to eradicate, and not selected for.

A black sable x black sable mating would be sable and black, no black & tans, 50% black sable, 25% sable, 25% black.  The homozygous sable most likely lighter in coat appearance, like my dog Hutch.

That should also not be possible if the presence of recessive a in a sable always expresses as a black sable phenotype........ or does it?

Phenotype isn't a guaranteed indicator of recessive black, just a probable indicator.  There are dark sables without it, and light sables that have it.

Not suggesting it's a guaranteed indicator daryl.... just looking for examples of phenotype that disprove the theory that black sables are always aw a.  The most likely scenario would be for a tanpoint to be born from a black sable x black sable mating, as tanpoint is by far the most common A series allele in the breed.

 If you have photos of the above examples, I'd love to see.  Thanks.

http://www.hellwiggshepherds.com/eros.html American show line black sable.

Question, I have a cezch line black sable, she carries for black, both parents were black sable. If I breed her to a solid black will I get black sable?

Yes you could get black sables but not regular sables if this theory is correct.  The expected ratio would be 1:1 black sable:black.

Thanks for the link.  Yes, again support for this.

"just looking for examples of phenotype that disprove the theory that black sables are always aw a."

I've seen many verifiable examples that would disprove it, I just don't recall any specific ones.