Figure 2.

Type 1 and type 2 damage–induced transitions. Circled letters represent the principle modifications observed in cloned sequences (e.g., deamination of C→U [read as T] or A→HX [read as G]). Changes introduced on the complementary strand when the damaged bases are subsequently copied are shown in italics. By convention, sequences are referred to in the L-strand orientation. Therefore, if an amplified sequence was initiated from an original H-strand template, then the type 1 and type 2 errors observed are expected to be T→C and G→A, respectively.