Fig. 3. Mutation spectra in the rpoB gene (RNA polymerase β) within codons 509–574 from rifR colonies, spontaneous (VEC) and after expression of UDG (only wild type), CDG or TDG. Codon positions are given on the X axis, and the number of mutations are given on the Y axis. The n value at the top left corner gives the total number of sequences. The mutations are classified as GC transitions (black bars), AT transitions (white bars), GC transversions (checked bars) and AT transversions (striped bars). The type of transitions and transversions, given as numbers as well as percentages, are specified at the top right corner of the spectra. In the recA mutant, only the spontaneous mutation spectrum was analysed.