Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Ihnestr. 73 and Mathematics and Computer Science, Free University of Berlin, Takustr. 9, 14195 Berlin, Germany. utz.pape@molgen.mpg.de|Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Ihnestr. 73 and Mathematics and Computer Science, Free University of Berlin, Takustr. 9, 14195 Berlin, Germany. utz.pape@molgen.mpg.de|Computational Molecular Biology, Max Planck Institute for Molecular Genetics, Ihnestr. 73 and Mathematics and Computer Science, Free University of Berlin, Takustr. 9, 14195 Berlin, Germany. utz.pape@molgen.mpg.de