Distribution of essential genes in S. pombe, S. cerevisiae and C. elegans. From this study, we estimated the percentage of essential genes in the S. pombe gene classes Ia (both yeasts + metazoa + plants + prokaryotes), Ib (both yeasts + metazoa + plants), and III + V (one or both yeasts). The distribution of S. cerevisiae essential genes was calculated from data in YPD (see Garrels 2002). The figures for C. elegans were adapted from Gönczy et al. (2000) who used RNA-mediated interference to investigate the percentage of essential genes in chromosome III: “multi-kingdom” genes (our class Ia), eukaryotic genes (Ib), and nematode-specific genes (that we classified under III + V). The essential genes that do not belong to any of the above classes were classified under “others.”
