Fig. 1

Secondary structure of RNAs. a Sketch of the secondary structure of yeast tRNA phe [45] (note the presence of four helices, three loops and a hinge). b Sketch of the secondary structure of the 5S rRNA [20] (note the presence of five double helices, four loops, and a hinge). In each case nucleotides are the black points, double helices are the regions with connections between opposite nucleotides and loops are the “circular” regions without connections between opposite nucleotides