Detection of chimera in three transgenic lines (from T1 to T3) of tobacco transformed with the binary vector pBin19-35SGusintron, which carry both npt II and gus genes, using three different methods. A) Histochemical GUS staining of their apical leaves (leaf on the left is a non-transformed control). B) Determination of the relative amount of the nptII transgene, as compared with a non-transgenic control, in their apical (AL) and basal (BL) leaves using quantitative, real-time PCR. Four independent DNA extraction per line were used. C) Southern blot analysis of the nptII transgene in the apical (AL) and basal (BL) leaves of the same lines. The lane labelled (+) corresponds to the digested pBin19-35SGusintron vector.