School of Engineering and Computer Sciences (Bioinformatics Laboratory), Old Library, University of Exeter, Exeter EX4 4PT, UK. a.narayanan@ex.ac.uk|School of Engineering and Computer Sciences (Bioinformatics Laboratory), Old Library, University of Exeter, Exeter EX4 4PT, UK. a.narayanan@ex.ac.uk|School of Engineering and Computer Sciences (Bioinformatics Laboratory), Old Library, University of Exeter, Exeter EX4 4PT, UK. a.narayanan@ex.ac.uk