Figure 1.

Geometric properties of Watson–Crick and mismatched base pairs. This figure is based on x-ray crystallography of duplex B-DNA oligonucleotides. The striking geometric identity of the Watson–Crick A⋅T and G⋅C base pairs is not matched by the A⋅C protonated wobble and G⋅T wobble base mispairs or by the G(anti)⋅A(syn) base mispair. [Reproduced with permission from ref. 14 (copyright 1987, Springer, Heidelberg).]