Department for Bioinformatics, Max Delbrück Center for Molecular Medicine, D-13122 Berlin, Germany. schober@mdc-berlin.de|Department for Bioinformatics, Max Delbrück Center for Molecular Medicine, D-13122 Berlin, Germany. schober@mdc-berlin.de|Department for Bioinformatics, Max Delbrück Center for Molecular Medicine, D-13122 Berlin, Germany. schober@mdc-berlin.de|Department for Bioinformatics, Max Delbrück Center for Molecular Medicine, D-13122 Berlin, Germany. schober@mdc-berlin.de