CLUSTER-ANALYSIS OF THE GENETIC-HETEROGENEITY AND DISEASE DISTRIBUTIONS IN PUREBRED DOG-POPULATIONS

Purebred dog populations have been subject to strong selection which h as resulted in extreme differences between breeds and decreased hetero geneity within breeds, As a result, breed-specific inherited diseases have accumulated in many populations, The aim of this study was to ana lyse genetic heterogeneity in relation to the distribution of elbow dy splasia in labrador retrievers, portosystemic shunts in Irish wolfhoun ds, and hepatic copper toxicosis, in Bedlington terriers, Decreased he terogeneity was demonstrated in the multiple genetic interrelations in the three populations, Zn pedigrees containing seven generations of a ncestors, the average number of common ancestors in all pair-wise comb inations of dogs was five to six (range 0 to 18), These complex interr elationships were resolved by a cluster analysis on matrices of relate dness, This analysis gave clusters of highly related animals, the aver age relatedness of these clusters, and the average relatedness of the entire population, as expressions of its genetic variability, The mean relatedness was 0.032 for Irish wolfhounds and Bedlington terriers, a nd 0.002 for labrador retrievers, The labrador retriever cohort was re solved into 31 clusters, and all cases of elbow dysplasia were concent rated in five highly related clusters with an overall incidence of 17 per cent, The Bedlington terrier cohort consisted of 12 clusters which all contained cases of copper toxicosis, with an overall incidence of 16 per cent, The Irish wolfhounds were divided into 14 clusters with a disease incidence of 1 per cent, Dogs with portosystemic shunts were found in four averagely related clusters, A genetic distribution beca me obvious only when relatedness due to common ancestors of the cases was used as a criterion, and the cases were then concentrated in five highly related clusters.