(a) All microRNAs in the mir-134 cluster appear to have arisen from a common ancestral sequence. The individual paralog groups have diverged rapidly in the ancestor of extant eutherian. Surprisingly, there is very little sequence variation between human and rodents in each of the paralog groups. The six families of alignable microRNAs are indicated in color. (b) WPGMA dendrogram derived from pairwise z-scores of the members of the mir-35 cluster. The analysis of the mature sequences demonstrates that the members of the cluster probably have arisen by means of tandem duplications.