FIG. 2.

The results of transposition assays indicate that the U5-IR stem was required for Tf1 transposition. (A) Substitutions of nucleotides and their positions in the U5-IR stem loop of Tf1 mRNA. The single-point mutations are 1, C124G; 2, C126G; 3, G128C; 4, C158G; 5, G160C; and 6, G162C. The double-point mutations are combinations of mutations 1 and 6, 2 and 5, and 3 and 6. (B) Transposition activity as indicated by growth on G418-containing plates. The agar plate shown contained the transposition assay patches of strains that contained the mutations shown in panel A. WT, strain with a wild-type version of Tf1.