We study the accuracy of a Bayesian supervised method used to cluster individuals into genetically
homogeneous groups on the basis of dominant or codominant molecular markers. We provide a formula relating an error
criterion to the number of loci used and the number of clusters. This formula is exact and holds for arbitrary number of
clusters and markers. Our work suggests that dominant markers studies can achieve an accuracy similar to that of
codominant markers studies if the number of markers used in the former is about 1.7 times larger than in the latter.