Transposition activity of Tc1/mariner elements upon CpG methylation. CpG-methylated (black bars) or untreated (grey) Tc1-, Himar1-, Hsmar1-, Minos-, SB-, FP-gene trap donor plasmids were co-transfected with/without transposase into HeLa cells and selected with G418. The transposition ratio was calculated by dividing the numbers of G418-resistant colonies obtained in the presence of transposase by the number of colonies obtained in the absence of transposase. Error bars are the standard deviation; the asterisk indicates that the error bar cannot be displayed for FP (±38.6). FP: Frog Prince; SB: Sleeping Beauty.