Institute of Computer Science, University of Tartu, 50409 Tartu, Estonia Center for Computational and Integrative Biology, Massachusetts General Hospital, Boston, MA 02114, USA.|Institute of Computer Science, University of Tartu, 50409 Tartu, Estonia.|Institute of Molecular and Cell Biology, University of Tartu, 51010 Tartu, Estonia.|Institute of Computer Science, University of Tartu, 50409 Tartu, Estonia.|Institute of Computer Science, University of Tartu, 50409 Tartu, Estonia.