Bioinformatics Group, Department of Computer Science, University College of London, London, WC1E 6BT, UK. a.koussounadis@cs.ucl.ac.uk|Bioinformatics Group, Department of Computer Science, University College of London, London, WC1E 6BT, UK. a.koussounadis@cs.ucl.ac.uk|Bioinformatics Group, Department of Computer Science, University College of London, London, WC1E 6BT, UK. a.koussounadis@cs.ucl.ac.uk