Computational Molecular Biology Max Planck Institute for Molecular Genetics, Ihnestrasse 73, D-14195 Berlin, Germany. gupta@molgen.mpg.de|Computational Molecular Biology Max Planck Institute for Molecular Genetics, Ihnestrasse 73, D-14195 Berlin, Germany. gupta@molgen.mpg.de|Computational Molecular Biology Max Planck Institute for Molecular Genetics, Ihnestrasse 73, D-14195 Berlin, Germany. gupta@molgen.mpg.de|Computational Molecular Biology Max Planck Institute for Molecular Genetics, Ihnestrasse 73, D-14195 Berlin, Germany. gupta@molgen.mpg.de|Computational Molecular Biology Max Planck Institute for Molecular Genetics, Ihnestrasse 73, D-14195 Berlin, Germany. gupta@molgen.mpg.de