Simplified two-gene model: B (Black/Chocolate) × D (Dense/Dilute).
Rabbit coat color is determined by 5 main gene loci: A (agouti pattern), B (black vs chocolate), C (full color to albino series), D (dense vs dilute), and E (extension — allows or restricts color). This simplified calculator uses the B and D loci: B_ D_ = Black, B_ dd = Blue, bb D_ = Chocolate, bb dd = Lilac. The full system produces hundreds of color varieties. Crossing two Bb Dd parents (Black carrying chocolate and dilute) yields the classic 9:3:3:1 ratio — 9 Black : 3 Blue : 3 Chocolate : 1 Lilac. Understanding color genetics helps breeders predict litter outcomes and work toward desired show colors.