Fig. 2

A PCR-based strategy to detect deletions and insertions. (A) This representative gel identifies frameshift mutations in JTT1 strain revertant clones. PCR products were resolved on a 5% Polyacrylamide gel. Complete deletion (44 bp) results in a 160-bp fragment. Lanes 4, 5, 6, 9, 13, 14, and 16 have small frameshift mutations that are undetectable by this assay, while lanes 2, 10, 11, and 12 have large deletions and lanes 1, 7, 8, and 18 have insertions. Lanes 3, 15, and 17 illustrate short deletions. (B) Selected AluI digestions of revertant plasmid. Lane 1 contains the 100 bp marker, lane 2 contains the original cloning vector pBR325, lane 3 contains pBRCINR, the original plasmid used for transformation. Lane 4 contains plasmid with an insertion corresponding in size to lane 1 in Figure 2a. Lane 5 contains a deletion corresponding to lane 2 in Figure 2a. Lane 6 contains a frameshift mutation below the limit of detection of this assay, and lane 7 contains a small deletion. The restriction digestion analysis agreed with the PCR results in every case.