Complementary genes are those non-allelic genes which independently show a similar effect butproduce a new trait when present together in the dominant form. Supplementary genes are a pair of nonallelic genes, one of which produces its effectindependently in the dominant state while the dominant allele of the second gene is without any independent effect but is able to modify the effect of the former to produce a new trait. Duplicate genes are independent genes producing the same or similar effect.