Table 1.

The 12 geometric families of RNA base pairs

Each geometric base pair family is defined by the interacting edges of the bases and the relative orientation of the glycosidic bonds (columns 2-4). Abbreviations and symbols for representing each base pair family in text and secondary structures are shown in columns 5 and 6. Column 7 shows an abstract representation of each family using triangles to represent the bases, where the hypotenuse represents the Hoogsteen edge. The shaded cells denote base pairs in the cis orientation.