Back in 2000, two purebred GSDs (one registered with the AKC, the other with the German Shepherd Club Of Germany) were bred together and produced a litter that included a puppy with symmetrical white markings on her muzzle, chest, collar, belly, tail tip, and forelock. The puppy was named “Franka.”
The breeder had the University of California/Davis study a sample of Franka’s DNA which found the puppy to be a purebred German Shepherd Dog. However, further tests concluded that the cause of her remarkable coloring was the result of mutation of the KIT gene.
The KIT gene controls cell functions, and in Franka’s case, it inadvertently affected color. It’s believed that KIT mutated dogs can’t “carry” the gene with out expressing it. Unless a puppy randomly mutates the gene, one parent has to have a phenotypical (or visible) KIT mutation to produce offspring with the Panda coloring.
UC/Davis wrote of the mutation that in its “homozygous state, the Panda mutation is considered an early embryonic lethal as no live dogs with the pattern and with two copies of the mutation have been observed. Put another way, pups homozygous for the Panda mutation don’t develop in the uterus and are reabsorbed very early on.