Department of Computer Sciences, Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA. stacia@cs.utexas.edu|Department of Computer Sciences, Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA. stacia@cs.utexas.edu|Department of Computer Sciences, Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA. stacia@cs.utexas.edu