FIG 3.

Effect of local context on the transversion rate. Nucleotide overrepresentation at sites of G·C-to-T·A transversion in the pyrE gene is depicted by letter size (see Materials and Methods). In weighted (proportional) analyses, each site was represented as many times in the alignment as in the corresponding set of mutants. The four panels represent different analyses of hot spots (a and b) and cold spots (c and d), as follows: the top eight transversion hot spots (unweighted) (a), the same eight sites weighted according to event frequency (see above) (b), sites of G·C-to-T·A transversion recovered in the mutation spectra of ogg⁺ dbh⁺ strains but not observed in RJ803 (unweighted; 11 total) (c), and sites at which G·C-to-T·A transversion creates a stop codon which nevertheless has not been observed in any S. acidocaldarius pyrE mutation analysis (unweighted; eight total) (d).