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Coat Color with Genetic Background of the Icelandic Sheepdog
Originally published in AKC Gazette, June 2012 edition, Used with Permission
All dogs hair colors are derived from three basic colors: black, red and white. If the alleles for dilution on the I-locus are present, red is turning to yellow. And if on the B-locus both mutations b/b are present, black becomes brown. All these colors will only be visible if the Em allel on the E-locus is present. Em is also responsible for having a black mask. If both e mutations are present on the E-locus (e/e), the dog will have a cream color and no mask!
So, if we want to define the color of our ISD, we have to use the colors black, brown, red, yellow, cream and white.
Special attention must be paid to white. Cells (melanocytes) in the skin produce the color pigments, and in areas without pigment, the coat will be white. The S-locus is responsible for the production of pigment, and mutations of the S allele can result in various designs of white. The mutations of S are (in sequence of dominancy) si (Irish spotting), sp (piebald spotting) and sw. The existance of sw hasn’t been proven; it would result in almost completely white dogs with only a spot of color on the head and a couple on the body (like the Jack Russell terrier).
Not all white markings are genetically determined. Early on in the development of an animal, the melanocytes have to migrate from the central part (the back) of the body across the whole skin. It is possible that they do not reach the most distant areas, so these might stay unpigmented, and thus white. Think about the tip of the tail, the feet, the middle line of the chin, neck, belly and the muzzle (line shaped white). This so-called “peripheral white” has a tendency to disappear during maturation. It is not wise to mention this white when defining the coat color.
Irish spotting means, that a dog has more white than only the peripheral white. The dog can have a white collar, a white neck and/or belly and more white on the head, tail and legs. In this case the name of the coat color is extended with “and white”.
Finally, the piebald dog can demonstrate several patterns, but he is predominantly white, with colored areas scattered over the body. Parts of the back are also white.
Irish spotting is dominant over piebald; so si/sp looks like Irish spotting, but the dog is carrying the allele for piebald.
Naming the colors of a pup can be difficult, because the colors can change when growing up. However, it is possible to give a couple of guidelines.
If you are not sure whether the color is red or yellow, look at the area behind the ear. There you can see the final color quite well and early on. If the pup is black and you wonder whether it will get tan (red or yellow), look underneath the base of the tail. Or, if there is white at a leg, look at the boundery between black and white.
For detailed information see: www.theicelandicsheepdog.com. There you will also find an overview with nine steps to correctly define the color of the pup.
Donna R. McDermott, MPPA