S-Figure 1. A histogram showing that mRNA-tagging can enrich for both abundant mRNAs and rare mRNAs. To assess if mRNA-tagging is severely biased for enriching abundant mRNAs, we estimated the quantity of mRNA for each of the 1329 L1 muscle genes (red bars). We compared the distribution of the estimated muscle mRNA quantity to the distribution of the estimated quantity of all mRNAs considered on the array (yellow bars). The quantity of the mRNA for each gene is estimated by calculating the net fluorescent signal from the channel representing the cell-free lysate mRNA on microarrays, and averaging this value over the six L1 muscle mRNA-tagging repeats. For each gene considered, the averaged net fluorescent signal was thrown into bins. The number in each bin was log10 converted and plotted.