Figure S4. (A) Scheme for construction of meta-genes. We start by performing an all-against-all blast of every protein sequence in one organism against every protein sequence in all of the other organisms. We then record the best BLAST hit for each gene with an E-value less than 10-5 (left; directed arrows indicate best BLAST hits). We ignore all non-reciprocal BLAST hits (middle), and identify meta-genes as connected components in the resulting graph. (B) Meta-gene multiplicity. Shown is the number of meta-genes (y-axis) that contain a particular number of genes from a single organism (x-axis). For example, there are 5289 meta-genes that included a single human gene, and 590 meta-genes that each included two human genes. Two meta-genes contained four human genes and a single meta-gene contained four fly genes. No meta-genes contained more than four genes from a single organism.