Figure 1.

The mutational spectrum. The sequence is that of the nontranscribed strand of the pyrE gene, with mutations of small extent shown above this sequence. A, T, G, and C denote BPSs. ▿ denotes a single-base insertion of a base identical to the base or bases below the symbol, except for the insertion of a G between T446 and T447 and the insertion of either three or six bases into the dotted-underlined sequence-fugue “CTACTACT” (for which we show only one of many possible insertions, as explained in the text). The five heavy underlines denote sequences that were tandemly duplicated. Δ denotes a single-base deletion of a base identical to the base or bases below the symbol. In the top line a deletion of 20 bases is shown comprising 17 bases (lightly underlined) between two triplet repeats (dotted underlined), one of which is also deleted.