Bioinformatics Research Centre, Department of Computing Science, University of Glasgow G12 8QQ, UK. jmorriso@dcs.gla.ac.uk|Bioinformatics Research Centre, Department of Computing Science, University of Glasgow G12 8QQ, UK. jmorriso@dcs.gla.ac.uk|Bioinformatics Research Centre, Department of Computing Science, University of Glasgow G12 8QQ, UK. jmorriso@dcs.gla.ac.uk|Bioinformatics Research Centre, Department of Computing Science, University of Glasgow G12 8QQ, UK. jmorriso@dcs.gla.ac.uk