Max Planck Institute for Molecular Genetics, Berlin Center for Genome Based Bioinformatics, Ihnestr. 73, D-14195 Berlin, Germany. Claudio.Lottaz@molgen.mpg.de|Max Planck Institute for Molecular Genetics, Berlin Center for Genome Based Bioinformatics, Ihnestr. 73, D-14195 Berlin, Germany. Claudio.Lottaz@molgen.mpg.de