Cocker Spaniel Coat Color Inheritance

The K series of genes acts on the "E" gene locus (normal dominant) in conjunction with the Agouti series of genes
To be visibly expressed the K gene must have at least one "E" (normal dominant) gene (non buff/red)
An "ee" (recessive buff/red) dog will be buff/red regardless of any K or Agouti genes
(taking this into consideration the rest of this explanation will treat the "e recessive" genes as if they didn't exist)

Whether any Cocker Spaniel is or carries either of the black or brown genes is inconsequential to this discussion, as these genes are independent of the K and Agouti genes and will all be referred to as black
Also disregard the piebald, chinchilla,merle, ect.
 

The K genes are: KB = black = dominant black kbr = brindle ky = yellow

The K genes in order of dominance: KB Black is dominant to kbr brindle and ky yellow kbr brindle is dominant to ky yellow  ky yellow is the most recessive of the color modifying K genes so must be homozygous to be expressed

The effect of individual K genes are:
K^B only allows the black on the "E" locus to be expressed and is completely dominant to any action of the Agouti series, so by default disallows any yellow pigmentation of the agouti genes, all Cocker Spaniels would be black
All dogs having K^BK^B, K^Bk^br, K^BK^y or K^Bk^y would have a coat color of black, no other color would be possible

The k^br  allows the agouti a^t and a^y to be expressed but only as brindle
All Cocker Spaniels having k^brk^br, k^brK^y would have a coat color of brindle if also carrying a^ta^y or a^ya^y, a Cocker Spaniel carrying a^ta^t would have brindle points instead of tan

The K^y creates yellow so the agouti genes can be expressed normally
All Cocker Spaniels having k^yk^y would have a basic coat color of yellow

The K genes only have an influence on those colors in the agouti series
The K gene series produces or disallows the distribution of yellow pigmentation on agouti, depending on which of the K genes are present with any particular set of Agouti genes

Conclusion:
As we know there are more colors than black and buff/red in cockers, and that they do have Agouti (tan pointed and sable) so we can determine that Cocker Spaniels do not have the K^B Dominant Black gene ( if carrying K^B none of the Agouti series would be visible )

We also know that cockers do not come with the phenotype of Brindle(yet?)
yet has already come and gone, I have responses from the  CkrGenetics@yahoogroups.com @ CkrGenetics indicating that there is k^br  brindle in American Cocker Spaniels), so we can determine ^{(updated Aug 16 2007)} that most
Cocker Spaniels do not have the k^br Brindle gene SEE EMAIL LINKS
(if you are a long time Sable Cocker breeder I'm sure you have seen newborns with stripes on their ribs right after birth, but this does not constitute the brindle color, as it is gone in a day or two and never returns)
 

This leaves us with only one choice k^y, which allows sable and tan points to be expressed, so we can determine that Cocker Spaniels do have the k^y yellow recessive homozygously.
This leads us to a more thorough understanding of Agouti inheritance and which can be calculated with simple Mendelian logic
 
 

This translates to;
For most cocker breeders this means no change in the way they plan for color breeding (cockers don't have dominant black or brindle, so they are of no concern)
For some (me), we must rethink the Agouti Series of genes in cockers
see related articles Black, Tan and Sable, Buff, Sable bred Buff

gary

visit
Sheila M. Schmutz web site; Genetics of Coat Color and Type in Dogs

Reference read it yourself
Linkage and segregation analysis of black and brindle coat color in domestic dogs
http://www.genetics.org/cgi/rapidpdf/genetics.107.074237v1.pdf  35 pages
right click 'save target as' or 'save link as'
you may need Adobe PDF reader