Division of Computational Molecular Biology, Max-Planck-Institute for Molecular Genetics, Ihnestr. 73, D-14195 Berlin, Germany. heydebre@molgen.mpg.de|Division of Computational Molecular Biology, Max-Planck-Institute for Molecular Genetics, Ihnestr. 73, D-14195 Berlin, Germany. heydebre@molgen.mpg.de|Division of Computational Molecular Biology, Max-Planck-Institute for Molecular Genetics, Ihnestr. 73, D-14195 Berlin, Germany. heydebre@molgen.mpg.de|Division of Computational Molecular Biology, Max-Planck-Institute for Molecular Genetics, Ihnestr. 73, D-14195 Berlin, Germany. heydebre@molgen.mpg.de