Structure of plasmid vectors, donor pB CMV-neo-EGFP (A) and helper mPBase (B); pB 5’TR, pB transposon 5’ terminal repeat element. pB 3’TR, pB transposon 3’ terminal repeat element. CMV, CMV promoter. neo, neomycin-resistant gene. EGFP, enhanced green fluorescence protein gene. Probe, the probe used for Southern blot. bGH polyA, bovine growth hormone gene polyA. (C). Surviving fetal fibroblast colonies in 10 cm dishes after transfection with linearized pEGFP-N1 or co-transfection with donor vector pB CMV-neo-EGFP and helper vector mPBase, and 2 week selection with G418. The pictures of the dishes with G418-resistant cell colonies were taken under blue light. (D). Colony count of G418-resistant cells in the dishes. The experiment was performed in triplicate and the data is presented as mean ± SD. A mean of 10 and 309 colonies was observed in cultures transfected with linearized plasmid pEGFP-N1, or co-transfected with donor vector pB CMV-neo-EGFP and helper vector mPBase, respectively.