1. From the University of Wisconsin-Madison, School of Veterinary Medicine, 2015 Linden Drive; and the Department Biostatistics and Medical Informatics (Broman), 1300 University Avenue, Rm 4710 MSC, Madison, WI, 53706. Dr. Rice's current address is the University of Pennsylvania, School of Veterinary Medicine, 3900 Delancey Street Philadelphia, PA, 19102