Epistasis: Gene Interaction Ratios

A dihybrid Punnett cross, AaBb × AaBb, always produces the same 16 genotype combinations — but the phenotype ratio you observe depends entirely on how the two gene loci interact. This simulator renders the full 4×4 cross as a 3D grid of 16 coloured cells, one per offspring genotype, and lets you switch between the classic patterns of gene interaction: no epistasis (9:3:3:1), recessive epistasis (9:3:4), dominant epistasis (12:3:1), duplicate recessive / complementary gene action (9:7), duplicate dominant epistasis (15:1), dominant-and-recessive epistasis (13:3) and polymeric gene interaction (9:6:1). Every ratio, phenotype-class count and top-class probability shown in the panel is recomputed live from the 16 underlying genotype cells for the selected rule, not looked up from a table.