Both RPP30 synthetic construct and human genomic DNA NA10860 (Coriell Cell Repositories Camden, NJ) were quantitated using the RPP30 assay on a digital array. Different amounts of RPP30 synthetic construct was then added into the genomic DNA so that mixtures with ratios of RPP30 to RNase P of 1:1 (no spikein), 1:1.5, 1:2, 1:2.5, 1:3, and 1:3.5 were made simulating DNA samples containing 2 to 7 copies of the RPP30 gene per diploid cell.