Number of essential genes covered by 22, 40, 71, and 115 mutant alleles. (A) The number of essential genes covered by 22, 40, 71, and 115 mutant alleles for the GPI-anchor pathway. Histograms represent the simulative probability distribution of the covered gene numbers using CDS length-dependent mutation rates. Expected values and experimental data are compared at the bottom of each panel. Notably, the expected values based on the CDS length-dependent mutation rates are more consistent with the experimental data than those based on the identical mutation rates (see Additional file 8: Figure S5). (B) The simulated number of genes covered by 407 mutant alleles.