Genes are traits possessed by mutants. When one gene trumps another in its own class it does 25% more damage (Strong) to it and 25% less damage (Weak) to the gene which trumps it.
Initially 3 basic genes are introduced which have 25% relations to each other:
Another triangle of 25% relations is introduced later:
Beyond that though, instead of the 25% Strong/Weak dichotomy it introduces the 50% Pathetic/Brutla dichotomy of interaction between the basic trio and the advanced trio.