Department of Computer Science and Center for Genome Sciences, Washington University, St. Louis, MO 63130, USA. davidlu@wustl.edu|Department of Computer Science and Center for Genome Sciences, Washington University, St. Louis, MO 63130, USA. davidlu@wustl.edu|Department of Computer Science and Center for Genome Sciences, Washington University, St. Louis, MO 63130, USA. davidlu@wustl.edu|Department of Computer Science and Center for Genome Sciences, Washington University, St. Louis, MO 63130, USA. davidlu@wustl.edu