G:U wobbles in the transforming growth factor-β receptor 2 (TGFBR2) 3' untranslated region (UTR)/small interfering (si)RNA sequence matches were over-represented in siRNA hits compared with siRNA non-hits, and were position- and strand-specific. (A) Nucleotides observed in individual siRNA positions, shown as the ratio of the frequencies in TGFBR2 siRNA hits with unique seeds (n = 92) to frequencies in the entire siRNA library. (B) TGFBR2 siRNA hits had more TGFBR2 3' UTR seed matches containing a G:U wobble at selected positions of the seed region than siRNA non-hits. Enrichments are shown for G and U in individual positions of the siRNA guide strand. P-values were calculated by Fisher's exact test.