Figure 2.

(a) Schematic illustration of a pairing between two monokaryons, where each monokaryon dilutes its genetic constitution by the acceptance of a nucleus and compensates for the dilution by simultaneously donating a nucleus to its partner monokaryon. (b) As in a, with the difference that one of the monokaryons has gained a mutation that prevents dilution of its genetic constitution, by inducing asexual reproduction or sexual reproduction via selfing, while still being able to donate a nucleus. While the ratio of black and white genome after pairing has changed from 1 : 1 to 2 : 1, the ratio of black and white genome in the spores has changed from 1 : 1 to 3 : 1, assuming that both parts of the mycelium produce equal numbers of spores.