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Originally Posted by paulapoo  Forgive my ignorant question. Does that mean that a yorkie with a white blaze on chest is likely to have the piebald gene? |
No Paula it doesn't. The piebald recessive gene is hidden and just by looking at a dog you cannot tell if they have this gene. It is all in the genetics each dog carries and unless you breed two dogs that both have this recessive gene and a litter is born with some of the puppies having white where other colors should be you would not know. The piebald recessive gene is in horses, cows, & pigs also. This is about genetics and is not breed specific. Breeders of any of these animals who are actively breeding for these results should understand this as it could carry potential health risks generations later if they are not educating themselves on these genes.
In the case of both the Biewer’s and the Parti’s they can trace their lineage back to many generations of Yorkies which is why the AKC had to accept the Parti’s here in the U.S. The Biewer’s were accepted by the UCI and have a breed standard.
Hopefully the following website will explain this further.
http://www.italiangreyhound.org/health/pragenetics.html
“Most genes have multiple "alleles" or choices that can be present at that site. Take the white markings in IG's for example. This gene has four alleles, solid, Irish marked, piebald (pied) and white. All IG's carry a copy of that gene that they inherited from each parent. Some have two copies of the Irish allele, some have two copies of the pied allele, and some have one copy of pied, and one copy of Irish. A dog that has one of each appears Irish (his phenotype), because the Irish gene is dominant and the pied gene is recessive. So when we see the dog, he is Irish, but actually his genotype is Irish with a pied recessive. When we breed this dog, he may produce pieds, since he is carrying the pied recessive. His phenotype does not reveal the true story of his genotype, and by looking at the dog, we have no way of knowing by his appearance that he carries the pied gene. This is a common situation with a recessive gene.
Here is another site which also explains it and the paragraph at the bottom explains the direction DNA testing is going for these markers.
http://homepage.usask.ca/~schmutz/dogcolors.html