1. Department of Food Science and Nutrition, School of Agricultural Sciences, The University of Zambia, Lusaka P.O. Box 32379, Zambia
2. Biomedical Sciences Department, Tropical Diseases Research Centre, Ndola P.O. Box 71769, Zambia
3. Laboratory of Genetics, Wageningen University & Research, P.O. Box 17, 6700 AA Wageningen, The Netherlands