Chromosomal location of replication origins (blue replication origins) and ORFs from cluster 13 (red dots). A randomization test revealed that the average ORFs are much closer to the replication origins than would be expected by chance. (a) The actual and expected average distance between ORFs and replication origins are shown with red lines to the left and right, respectively. The variation of the expected distance is indicated with a black histogram. (b) The genomic position of genes in cluster 13 (red dots) and replication origins (blue stars).