[pstinard]

Originally Posted by pstinard

Well, before I read that article, I had assumed that Biewers and Partis were both carriers of the piebald allele at the MITF gene because they supposedly both traced back to Streamglen (is that true, or just a theory that both trace back to Streamglen?). Now that some Partis have tested as "e" at the E gene, I'm not so sure. Biewers are definitely piebald, but maybe some lines of what people are calling Parti are piebald and others are "e"? I don't know--more testing of Partis is needed! Have any Parti breeders here had their dog's coat color genes tested?

What makes a dog lineage a separate breed is a unique appearance and genetic uniformity that is distinct and separates them from other breeds. The 100 Biewers that were tested in the MARS study fit that description because they could be separated from the Yorkshire Terrier group in the Primary Component Analysis. But those Biewers are from Biewer by Biewer matings, so that kind of breeding has kept them separated from the Yorkshire Terrier gene pool. The breeders who cross Biewers with Yorkshire Terriers to create "splitters" are breeding more Yorkshire Terrier into their DNA and they will test to be more like Yorkshire Terriers and may not be separable from Yorkshire Terriers by the MARS test.

To recap:

Beiwer X Biewer = separate breed

Biewer X Yorkshire Terrier = becoming more like Yorkshire Terrier, and are not a separate breed.

Parti X Parti = No data on that, sorry!

Parti X Yorkshire Terrier = becoming more like Yorkshire Terrier and not a separate breed.

Chocolates -- No data on them either, but if they are being crossed back to Yorkshire Terriers, they are becoming more like Yorkshire Terrier and not a separate breed.

The upshot is that these colors were all bred into Yorkshire Terriers from some other breed in the (hopefully distant) past, and just because a dog is a different color, doesn't automatically make it a different breed. What makes a dog a different breed is more than just a single coat color gene--it involves multiple genes on multiple chromosomes that have become fixed by breeding within the emerging breed or population to keep it separate from other breeds, and you have to be able to distinguish the separate breed from other breeds by appearance, behavior, etc.

"Principal Component Analysis," not "Primary Component Analysis," but it's too late to fix by editing.