Fig. 2
From: Assessment of assumptions underlying models of prokaryotic pangenome evolution
Venn diagrams illustrating how violation of either one of the IGP-CGS assumptions will reduce the number of singletons. The number of singletons can be extracted from gene intersections using Eq. 3 (a). When the assumption of an infinite gene pool is violated, genes can be regained into the intersection regions of the diagram, resulting in less singletons (b). Within the IGP-CGS model, the genome size is maintained by a balance of gene gain and gene loss events. When there are more gene losses than gene gains, the genome size reduces, decreasing the number of singletons (c)