Clusters of OR genes. A region of human chromosome 11 showing OR genes (green), the clusters annotated in the CLIC/HORDE database (blue) and the statistically significant clusters predicted by WordCluster (red). Our algorithm predicts more compact clusters compared to the CLIC/HORDE annotation. For example, in the first and third HORDE clusters pronounced gaps exist between the genes, which is detected by WordCluster but ignored by the CLIC/HORDE annotation. The figure was generated using the UCSC Genome Browser .