Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA.|Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA.|Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA.|Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA.|Computational Biology Department, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, USA.