MicroRNAs of Worms and Flies Figure 1. Clusters of mir genes in the C. elegans and D. melanogaster genomes. 35 of the 137 C. elegans mir genes (the 137 genes produce 139 miRNA forms) (A) and 60 of the 152 D. melanogaster mir genes (B) are situated within 2 Kb of each other on one of their chromosomes (6 chromosomes in C. elegans: Chr. I–V, Chr. X; 4 pairs of chromosomes in D. melanogaster: Chr. 2–4, X/Y). ,63% clustered mir genes in the C. elegans genome and ,38% in the D. melanogaster genome are related in sequence. Bounding boxes highlight clustered mir genes of conserved sequences at the 59 end (^) and/or over full length (#70 indicates $70% similarity) (see Tables 1, 2 and Datasets S1, S2, S4 and S5 for details). mir genes on the left or above chromosomes are found in the Watson strand whereas those on the right or below are located in the Crick strand. The physical centers of C. elegans chromosomes are indicated by ‘‘0’’. doi:10.1371/journal.pone.0002818.g001 PLoS ONE | www.plosone.org 18 July 2008 | Volume 3 | Issue 7 | e2818