Program in Computational Biology and Bioinformatics, Yale University, New Haven, CT, USA.|Department of Genome Sciences, University of Washington, Seattle, WA, USA.|Program in Computational Biology and Bioinformatics, Yale University, New Haven, CT, USA.|Department of Genome Sciences, University of Washington, Seattle, WA, USA.|Program in Computational Biology and Bioinformatics, Yale University, New Haven, CT, USA.