As a masking gene (& recessive), wouldn't the expression of white be an all or nothing phenomenon (barring the light cream shadings which are sometimes present). IF black is a true recessive, wouldn't it fail to express unless the dog is homozygous for it? Or are they more accurately co-expressed? Given that white dogs have normal dark pigment are they more prone to skin cancers? Are they really more prone to other genetic disorders?Quote:Good" breeders won't let a white breed into their lines. It is not only a Disqualifying fault, the white gene also DILUTES the colors of the following generations of dogs coming from that line. Breeding a white to a black/tan (or other accepted color) washes out the colors of the offspring. If allowed to continue, in a few generations 'normal' colors would be whipped out.
For this reason, the gene pool available to the white German Shepherd is very narrow. Because of this, they are more prone to genetic disorders. They also can get skin cancer, which normal color shepherds do not get.
The black dog will IMPROVE the pigment on any standard color dog it is bred to, so they are often used to breed with 'more usual' color German Shepherds.