These large structural changes can be detected using conventional technologies such as Southern blot and longrange PCR. However, it is believed that real-time PCR is Figure 1 . Quantitation of the RPP30 copy number in spike-in samples that contain two to seven copies of the RPP30 molecules per two haploid genomes. The x-axis shows the expected ratio of the numbers of RPP30 molecules to RNase P molecules. The y-axis shows the observed ratios. Each value is calculated using five panels of the same sample mix and the error bars represent standard errors. A good linear correlation can be seen with a coefficient of determination (R 2 ) of 0.996. currently the only promising technique that is able to provide information about the exact copy number of the CYP2D6 gene in a routine clinical setting (32) (33) (34) .