FIG. 2.

Southern blot hybridizations of pulsed-field gels across drug-cycled transfected lines. (A) 3D7-TKMSP4/5 chromosomes probed with hDHFR and pGem probes across four drug cycles. (B) 3D7-ΔMSP5 chromosomes across four drug cycles also probed in a Southern blot with hDHFR and pGem, indicating the loss of msp-5 in late drug cycles. A 3D7 genomic control was loaded in the leftmost lane of every blot, and the position of migration of chromosome 2 is denoted by the bars. Identical blots were hybridized with the hDHFR probe (positive selectable marker) and the pGEM probe (plasmid backbone). Loss of chromosome 2 signal (arrow) indicates double crossover integration. C, cycle.