1. Genetic Epidemiology, 391 Chipeta Way Suite D, Salt Lake City, UT 84108, U.S.A.
2. 10 Peterborough Drive, Sheffield S10 4JB, U.K.
3. Centre for Bioinformatics and Computational Biology, and Division of Genomic Medicine, University of Sheffield, Royal Hallamshire Hospital, Sheffield S10 2JF, U.K.