Liver, blue, grizzled coat colors, recently discovered K locus, a practical, understandable 3-part series, by scientist, breeder, International and AKC Judge
Canine Coat Color Genetics, Part 2
Liver and Blue Coat Colors
Fred Lanting, All-Breed Judge, SAAB, Sieger/Schutzhund
In Part One, I mentioned that a recently discovered chromosome location called the K locus, which has genetic information on (control over) such coat-color expressions as solid black, brindle, and part of the reason for tan markings. I also mentioned the “agouti” genes found at other chromosome locations that determine whether a dog will have a sable or wolf-like color pattern, or will be black-and-tan or “fawn-red.”
Many breeds include individuals that have what has been called sable markings, but this word has been used so differently to describe color phenotypes in various breeds, that a Collie owner may have a different image in mind than does a German Shepherd owner using the same word.
Words such as sable, saddle, tan-points, ticking, brindle, and dozens more can be daunting to the experienced dog fancier, so you can imagine how lost a novice might be in such a world of words. As a former educator, I recommend you exercise this maxim: Start with the simple before going on to the complex. In regard to coat colors, imagine that there are only two: black and brown. Don’t get ahead of me, now. White is technically not a color, but the absence of color. Also, there are diluted variations of those two basic colors, which we are discussing in the coming paragraphs.
You have seen many dogs with a “grizzled” look in part of their coats. Various genes tell the cells (in hair, for example) how to arrange pigment granules so that their groupings can give the appearance of striped or banded hairs (alternating dense granules, then fewer or nearly none) or uniformly dark. This “banding” can make one dog look much lighter over-all than another dog that also has the coding for “dark” (black, liver/chocolate, blue) hairs throughout more of the coat.
This segregation of “clumps” of pigment granules into parts of the hair shaft in order to give bands or tips of black is not the same thing as the “thinning-out” of melanin particles in such shafts that gives one or the other of what we call “dilute” colors. These are “blue and “liver” but they each have a number of other popular names. The alleles (gene varieties) that give these dilutes of black are on different chromosomes, so it is possible for a dog to have both.
The Weimaraner has been considered to have the “dilute black to blue” instruction gene on one chromosome and the “dilute black to liver” instruction on another chromosome, this combination resulting in its characteristic silvery coat color as well as integument (nose, lips, anus, etc.). This combination also occurs in the Doberman, in which case it is referred to as blue or an “Isabella”. It can occur in any breed in which both liver and blue are allowed.
To see if a phenotypically brown dog or a white dog has one type of these dilutions, look at those integument areas, since there is no “black area” in the coat. Such locations give away the genetic make-up in such dogs whose haircoat gives no clues.
Both of these dilutions are recessive to full black expression, which means that in order for a dog to show blue coat, it must have inherited two blue-dilution genes (called alleles), one from each parent. Similarly, a liver-nose dog must inherit the liver dilution gene from both parents. The liver or blue color will not only show in the integument, but will also be seen in whatever part of the haircoat would otherwise be black.
Dilutes such as liver (chocolate), blue, and Isabella/lilac are pictured. For more explanation of the letter designations for genotype, such as atatbbddebeb, see my other articles on genetics.
Fred Lanting is an all-breed judge with experience in over 30 countries. He is a well-known Shiba breeder and GSD authority. He handled Akitas in the 1960s and `70s, and was named an official JKC judge, a rare honor. He has lectured around the world on breeding, judging, canine movement, and CHD (canine hip dysplasis). Be sure to peruse these Dog Books by Fred Lanting
Courtesy NetPlaces Network