Population structure of purebred dogs and Alaskan sled dogs. The cluster analysis of 21 purebred breeds [10, 11] and two Alaskan sled dog populations grouped by the racing style (sprint or distance). For each breed we utilized DNA samples from five individuals who were unrelated at the grandparent level. Individuals grouped into breed-specific clusters, denoted as differring colors on Figure 2, based on the percentage of their allelic pattern belonging to the specific cluster. The two Alaskan sled dog groups created their own populations based on their unique genetic signature of microsatellite-based markers.