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In genetics, dominance relationship refers to how the alleles for a single locus interact to produce a phenotype. For example, flower color in sweet peas (''Lathyrus odoratus'') is controlled by a single gene with two alleles. The three genotypes are PP, Pp, and pp. The flower color for PP (purple) and pp (white) do not depend on the dominance relationship. However, the heterozygote Pp could theoretically have many different colors, e.g., purple, white, or a light purple. The color of flowers produced by the heterozygous plants depends on the dominance relationship between the two alleles in question.