Duplicate Genes - The presence of a single dominant allele of anyone of the two genes governing the trait produces the dominant phenotype. The recessive phenotype is produced only when both the genes are in the homozygous recessive state, i.e., the dominant genes when present together or alone will produce the same phenotype, but when they are in recessive state together, they will produce different phenotypes. This gene interaction produces a ratio of 15:1.

.For example, the non floating habit in rice is controlled by two dominant genes DWI and DW2' When a non floating rice strain with the genotype (DW1' DW1' DW2' DW2) is crossed with a floating strain (dw1' dw1' dW2' dw), the Fl is non floating.