In PLOS Genetics, members of the Wisdom Panel Research Team from Finland, the US, and the UK describe Mendelian disease-associated variant patterns found in nearly 1.1 million mixed-breed or purebred dogs with commercial panel screening data, demonstrating that Mendelian disease variant load tends to rise as heterozygosity drops across the dog genome. Using array-based genotypes spanning 250 Mendelian disease-related variants in 811,628 mixed-breed dogs and 242,665 purebred dogs — together with electronic medical records for almost 44 percent of the dogs — the researchers unearthed 207 of the variants in question, uncovering at least one copy of a risk variant in 57 percent of the dogs. Along with clues to variant penetrance and clinical significance, their analyses offered a look at variants and corresponding conditions found within and across breeds, including dwarfism- and short limb-related variants that appear more common in mixed-breed dogs. "We found that disease-associated variants are collectively common in dogs and that many health issues are shared by both mixed-breed and purebred dogs," the authors report. "Our study also emphasizes the importance of avoiding excessive inbreeding in dogs by associating lower genetic diversity levels with an increased risk for the manifestation of inherited diseases."