Analysis of excision and insertion events. Analysis of the mPing excision sites from ADE2 revertants by polymerase chain reaction (PCR) using flanking primers and digestion with HpaI (A). mPing excision results in smaller products that can only be digested with HpaI when the ADE2 gene is repaired perfectly. Some ADE2 revertant colonies carry both the original and excised versions of the reporter plasmids, resulting in the two PCR products shown. The HpaI site is underlined, the target site duplication (TTA) is shown in bold, and mPing sequence is italicized. (Neg = mPing reporter, Pos = ADE2) The mPing insertion preference in yeast is shown as a pictogram (height of letter indicates % at that position) and the frequencies of preferred nucleotides compared to rice  (B).