The secondary structure, generated by the
mfold Web Server available through http://frontend.bioinfo.rpi.edu/zukerm/home.html, for a 79 base fragment from the 3′ UTR of the 7440 nucleotide RNA virus poliovirus 1-Mahoney, Genbank Accession No. J0228140 [19]. The structure has two hairpin loops, two internal loops (one of which is a bulge loop of size 2), one branching (multi) loop, and an external loop. The adjacent plane tree (rooted at the bottom) models the configuration of the RNA secondary structure, preserving information about the basic arrangement of loops/vertices and helices/edges.