We also introduced a single or triple adenosine bulge at either side of the stem, to investigate potential bending effects on frameshifting. Figure 3A and B show that the single adenosine bulge mutant decreased frameshifting, depending on the location of the bulge, five to seven fold compared to the 12 bp hairpin construct. When the bulge was enlarged to three adenosines the frameshifting was almost abolished. Interestingly, the effect of bulges at the 3 0 side of the stem was less dramatic than those at the 5 0 side.