1. The Roslin Institute and Royal (Dick) School of Veterinary Studies, Easter Bush, EH25 9RG, United Kingdom
2. Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DU, United Kingdom
3. Mater Research Institute-University of Queensland, Translational Research Institute, Brisbane, Qld 4102, Australia
4. Animal Genetics, 1336 Timberlane Rd, Tallahassee, FL 32312