Fig. (1) Electrophoretic mobility of representative plasmid DNA isolated from overnight cultures. Plasmid DNA isolated from E. coli transformants using the rapid boiling method [13] was fractionated on an agarose gel. Because the samples were not treated with RNaseA, RNA appeared at the bottom of the gel. Horizontal arrowheads (<) indicate the plasmid DNA showing size alteration. (A) pAL79 DNA isolated from JM107 transformants. Lane 1, sample containing normal pAL79 plasmid; lane 2, sample containing altered plasmid; lane M, HindIII-digested λphage DNA size markers. SC, supercoiled molecule; OC, open circle (relaxed molecule); SCD, supercoiled dimer molecule. (B) pAL79 DNA isolated from DH10B transformants. Each lane corresponds to a DNA sample isolated from an independent colony. The vertical arrow indicates the sample containing the altered plasmid DNA. Lane M, HindIII-digested λ phage DNA size markers. (C) pUC19 DNA isolated from DH10B transformants. Lane 1, sample containing normal pUC19 plasmid; lane 2, sample containing altered plasmid; lane M, HindIII-digested λ phage DNA size markers.