That is not all that uncommon but contrary to popular belief are hounds puropsely bred for white tail tip it is a natural phenonenom of pigment cell migration from the nural crest allong the spine. It is why it is typical for a dog if it is to have white to be on the chest, muzzle tip of the tail belly or feet. These are the furthest point form the nural crest. Unlike much of coat color genetics cell migration is effected by the environment such as temperature. So it is possible for two Identical twins to end up with different marking based only on where they were in the womb.He is the first basset or beagle I have ever seen that didn't have a white tipped tail
Wow, that is interesting, that means breeders could have identical dogs and not realize it (or have any way to really tell without genetic testing) because the tip of tail, muzzle and feet may be marked different.Unlike much of coat color genetics cell migration is effected by the environment such as temperature. So it is possible for two Identical twins to end up with different marking based only on where they were in the womb.
That would result in piebald or open tris or bi color ie one with more white rather than one with white in a specific area. It is not a matter of not having enough cells to migrate but rather how far they travel.So having not having enough pigment cells to migrate all the way to the tail could be bred for.
For example, in animals heterozygous for a loss-of-function mutation at
Ednrb, which encodes a receptor on melanoblasts that helps stimulate migration and proliferation, every cell in the animal has reduced gene dosage for Ednrb, which lowers the threshold for additional factors ± environmental, genetic, or random ± that may cause the death of an individual melanoblast. Thus, animals with identical Ednrb mutations have different amounts of spotting, and their spots are located in different regions of the body.
...While most white-spotting mutations produce localized deficiency of melanocytes in an irregular pattern that varies among genetically identical animals, mutations that produce a regular and stereotypic pattern of spotting are easily recognized in certain species, e.g., panda bears or weasels