Quote:
Originally Posted by pstinard  How these other breeds got mixed in Yorkshire Terriers to create the Biewer Terrier is somewhat a mystery to me (perhaps falsified pedigree records in the distant past or "oops" matings, but I am not going to point fingers because those people are long gone and we have no real way of knowing), but the DNA evidence is there, and it is very strong. For me, the smoking gun is the piebald spotting gene (MITF gene) on chromosome 20. This isn't a simple random mutation that can spontaneously occur over and over, but appears to have originated once during the domestication of dogs, and been transferred to the breeds with piebald spotting by crossbreeding and selection. In the breeds analyzed so far, all piebald spotting genes carry a unique DNA insertion called a SINE in the upstream regulatory region of the MITF gene (the part of the DNA that controls the expression of the MITF gene--where and when the gene will be expressed during the dog's growth and development) as well as a separate length polymorphism (segment of DNA that can vary in length) in the upstream regulatory region. The chances against both changes occurring at once spontaneously in a single Yorkshire Terrier are astronomical. My conclusion is that the piebald spotting gene had to have been bred in from another breed of dog during the development of the Biewer Terrier. The way to resolve this question once and for all would be to completely sequence the upstream regulatory regions of the MITF gene in Biewers and see whether it indeed carries the SINE and the length polymorphism. If it does, then it's a done deal as far as I am concerned that the Biewer arose from breeding a Yorkshire Terrier with another breed and re-extracing the piebald color gene. |
There is some controversy about other breeds potentially being mixed in by Mr. Biewer. I think it's the Maltese. But that suggestion has been disputed by many people.
In any event, I agree that crossing the Biewer back with the Yorkshire Terrier would water down the Biewer characteristics. I know many here are vocally against Biewer to Biewer breedings but I think it's the only way to preserve the Biewer breed as a distinct breed.
Thanks for your analysis. Tracey