Coefficient of variation (CV) plotted on Y axis and average depth per nucleotide (APN) on X axis. Points with average depth of greater than 1000 are not displayed. Panel A is D. simulans BR2 TR2. Panel B is D. melanogaster female heads BR2 TR1. Panel C is TR1 for cell line c 167. Note that despite the difference in the number of mappable reads, the pattern of CV against the mean remains the same. CVs are very large when the average expression is low. Individual points represent exonic regions (Flybase 5.4) cubic smoothing line fit using R's smooth.spline function.
McIntyre et al. BMC Genomics 2011 12:293 doi:10.1186/1471-2164-12-293