School of Biological Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PT, UK. selley@bioinf.man.ac.uk|School of Biological Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PT, UK. selley@bioinf.man.ac.uk|School of Biological Sciences, The University of Manchester, Oxford Road, Manchester, M13 9PT, UK. selley@bioinf.man.ac.uk