RNA editing sites characterized by the level of editing and their presence in multiple mouse strains. (a) The overall level of editing is determined by the number of reads with/without the edited base per site and is shown over all sites/strains (solid line). The variability in the level of editing is shown as the distribution of standard deviations (std dev) from average values at each site both within (dashed line) and across strains (dotted line). For example, 90% of all sites have 60% or fewer reads edited and the standard deviation for 90% of all sites is less than 10 to 15%. (b) The frequency of sharing of sites (solid bars) and clusters across the strains (dashed bars). The lines show the hypothetical number of shared edits/clusters when uneven coverage and expression are taken into account, as explained in text.