1. Department of Haematology, Bayero University Kano and Aminu Kano Teaching Hospital, Kano, Nigeria
2. Faculty of Health Sciences, Sydney Brenner Institute for Molecular Bioscience, University of the Witwatersrand, Johannesburg, South Africa
3. Molecular Genetic Epidemiology Section, Basic Research Laboratory, Frederick National Laboratory for Cancer Research, NCI, Frederick, MD 21701, USA