Department of Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Berlin, Germany. hafemeis@molgen.mpg.de|Department of Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Berlin, Germany. hafemeis@molgen.mpg.de|Department of Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Berlin, Germany. hafemeis@molgen.mpg.de|Department of Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Berlin, Germany. hafemeis@molgen.mpg.de