1. Bioinformatics Research Centre, Department of Computing Science, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.
2. Department of Computing Science, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.
3. Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.
4. Beatson Institute for Cancer Research, Garscube Estate, Switchback Road, Bearsden, Glasgow G61 1BD, Scotland, U.K.