Simulation results from a multiple-point mutation model for all the families when mr = 0.001. The horizontal axis indicates the simulation steps (generations). The vertical axis shows the average variation of the protein family measured as the average distance from the mutated amino acid sequences, at a particular time (generation number), to their respective reference sequences. Each curve refers to the average variation response of a family to multiple-point mutations. Top and bottom curves represent the average variation of DGF1 and nuclear amino acid sequences respectively.