Fig 2. Theoretical protection from mutations conferred by overlapping reading frames.

Simulated protection conferred by a gene overlap, depending on the size of the overlap and the fraction of frameshift mutations. The protection is the fraction of loss-of-function mutations in the costly gene that are purged due to the pleiotropic cost induced by the overlap. A true protein overlap (dashed lines) would also protect from non-polar mutations. The average deleteriousness of each amino acid substitutions was P_e = 0.1 (the effect of other values of P_e as well as of alternative models of protein loss-of-function are shown in S2 Fig).