Efficiency of amplification of npt II and β-actin genes in three independent DNA extractions from A) apricot callus and B) tobacco leaves, transformed uniformly, with the binary vector pBin19-35SGusintron. Both apricot callus and tobacco plants harboured one copy of the transgene. DNA samples from transgenic callus and plants were diluted serially to obtain a standard curve for both the endogenous β-actin and nptII genes and the Ct value was plotted against log [DNA]. Samples were run in three replicates of each of the three independent DNA extractions. The correlation coefficient and slope values are indicated.