Total copy number of mRNAs was calculated for the 4,416 genes whose GSPs were validated for quantification (Additional data file 6). The same RNA samples as those shown in Table 1 were used for GATC-PCR quantification. Note that we excluded the genes whose expression levels were called to be zero from the calculation, because we could not distinguish between the genes that we failed to amplify from the cDNA template and those that were expressed at undetectable levels. Thus, the number of "genes quantified" in the table should be regarded as the most conservative or minimum estimate. To minimize the effect of failed assays, we merged the three datasets to cover 4,287 genes measured at least once in the three measurements and calculated the total copy number from the average copy number of each of these genes.