Fig. 2

Counting t _i -pairs. The three unfractionated progeny of gene g define three t _i -pairs, as indicated by three ovals. We follow the pair contained in the uppermost oval, as the two members at time t_i+1 independently (shaded triangles) evolve into \(m^{\prime }_{n}\) and mn″ genes, respectively, at time t _n , defining \(m^{\prime }_{n}m''_{n} t_{i}\)-pairs at time t _n