1. Institute of Molecular Biology and Physiology, University of Copenhagen, Sølvgade 83 H, DK-1307 Copenhagen K
2. Department of Biochemistry and Molecular Biology, University of Southern Denmark, DK-5230 Odense M, Denmark
3. Institut für Tierzucht, Bundesforschungsanstalt für Landwirtschaft (FAL), Höltystrasse 10, 31535 Neustadt-Mariensee, Germany