Centre for Bioinformatics, Division of Molecular Biosciences, Imperial College London, SW7 2AZ, UK. d.huntley@imperial.ac.uk|Centre for Bioinformatics, Division of Molecular Biosciences, Imperial College London, SW7 2AZ, UK. d.huntley@imperial.ac.uk|Centre for Bioinformatics, Division of Molecular Biosciences, Imperial College London, SW7 2AZ, UK. d.huntley@imperial.ac.uk|Centre for Bioinformatics, Division of Molecular Biosciences, Imperial College London, SW7 2AZ, UK. d.huntley@imperial.ac.uk