Remarkably, in WGE the IBV hairpin has been reported to induce high levels (34%) of frameshifting versus 51% for the IBV pseudoknot (24) . In that study modified extracts were used that are somewhat more frameshift-prone than the standard wheat-germ extracts. Nevertheless, the ratio between pseudoknot and hairpin-induced frameshifting in this system is also 1.5. This number may reflect the additional interactions, like base triples, in a pseudoknot that make it a better frameshift stimulator than a hairpin.