VARIABILITY OF CANINE MICROSATELLITES WITHIN AND BETWEEN DIFFERENT DOG BREEDS

Polymorphic animal microsatellites have proved valuable genetic marker s. For this project, the variability of 19 canine microsatellite loci was examined within and between three pure breeds of dog: Greyhounds, Labradors, and German Shepherds, The number of alleles, absolute and r elative frequencies, and the statistics that express polymorphism with in a breed were determined. The evolutionary relationships among these closely related dog breeds were estimated by genetic distance measure s developed for use with microsatellite loci. According to the pairwis e genetic distances, Greyhounds and German Shepherds had longer divers e evolutionary histories than Greyhounds and Labradors or Labradors an d German Shepherds, Although a few breed-specific alleles were observe d, the significant differences between breeds are in their relative fr equencies and distribution of the alleles across a locus. None of the three pure dog breeds corresponds to Hardy-Weinberg equilibrium. A con siderable reduction in intrapopulation variation was observed within t hree pure breeds. compared with the population of individuals belongin g to 15 dog breeds. This reduction was especially pronounced in the Gr eyhound breed, which expressed the lowest degree of variation. Intrapo pulation variations of Labradors and German Shepherds did not differ s ignificantly, that of Labradors being only slightly higher, The intras pecies variation of dogs is lower than in humans, mouse, or rat, but s imilar to that in domestic animals. probably reflecting similarly high inbreeding coefficients. However, some highly informative loci were c ommon to all dog breeds tested so far. Such population data are necess ary for mapping studies and linkage analysis in dogs. ployed in dog pa ternity testing (Zajc et al. 1994; Freedholm and Wintero 1995), in stu dies of differentiation patterns among various members of Canidae fami ly (Roy et al. 1994), and in conservation genetics (Gottelli et al. 19 94). In this project, we have investigated the genetic Variability wit hin and between three pure breeds of domestic dogs: Greyhounds, Labrad ors,and German Shepherds. Nineteen canine microsatellites loci, which are known to be polymorphic in mixed-breed dogs, were chosen from a ba nk of canine microsatellites, generated for use in DNA mapping studies and linkage analysis in our laboratory.