Distribution of dN/dS values among indel containing genes. The histograms show the measured distributions of gene frequencies with dN/dS values in binned intervals of length 0.1, starting from 0. Gene frequencies are generally peaked in the interval 0 ≤ dN/dS ≤ 0.1 and decay for larger dN/dS values, indicating strong purifying selection on protein coding regions throughout evolution. However, the distributions of the subsets of genes that contain at least one insertion/deletion decay slower compared to the background distribution of all analyzed genes.
de la Chaux et al. BMC Evolutionary Biology 2007 7:191 doi:10.1186/1471-2148-7-191