Selection of significant RNA structure groups. (A) Distribution of RSmatch scores for all-against-all pairwise comparisons of 6,345 human RNA structures. The cutoff value = 17, as indicated by a dotted vertical line. The distribution of scores for the selected structures (2,054 in total) is shown in the inset. (B) Hierarchical clustering of all 2,054 human RNA structures by the normalized dissimilarity score. For cluster analysis, we used the hierarchical clustering with the "average linkage" method for joining nodes. (C) One hundred normalized dissimilarity scores were used to cut the hierarchical clustering tree to obtain structure groups. Distribution of CoV vs. group size using real data (D) and randomized data (E). Horizontal lines in E are mean values for different groups, which were used as cutoff values for selecting structure groups for the real data.