Derived allele frequencies increase at multiple loci as body weight decreases. The frequency of the derived allele in 5-lb weight classes is represented on a color scale. The smallest dogs (bottom row) are consistently red at all markers except IGF1R, while the largest dogs rarely carry a derived allele, as observed in weight classes of 90–95 (40.8–43.1 kg), 95–100 (43.1–45.4 kg), and above 105 (47.6 kg). The high frequency of the IGF1 derived allele in the 100–105 class represents the only breed we tested in the class, Rottweilers. Dogs with an SBW above 105 lb are collapsed in a single category due to the lack of genotype variation in the group at these markers. This analysis includes all 500 dogs genotyped.
