Paternity testing with genetic markers: are Y-linked genes more efficient than autosomal ones?

The average probability of exclusion for a Y-linked locus is computed and compared with that for an autosomal locus. It is shown that even if a Y-linked locus is only marginally polymorphic, it considerably enhances the chance of paternity exclusion in paternity dispute cases involving sons. For the positive identification of paternity, a Y-linked marker is not necessarily more ideal than an analogous autosomal marker since the discrimination of true fathers from random men not excluded from paternity (RMNEP) is still difficult on the basis of a paternity index. It is concluded that Y-linked markers are more efficient for paternity exclusions of male children, while for the positive identification of paternity their advantages over the autosomal markers are questionable.