partial dominance In genetics, incomplete or semi-dominance; the production of an intermediate phenotype in individuals heterozygous for the gene concerned. Partial dominance is generally considered to be a type of incomplete dominance, with the heterozygote resembling one homozygote more than the other. For example, in Mirabilis jalapa (the marvel of Peru or four-o'clock plant), individuals with red petals bred in a pure line when crossed with a pure line with white petals will yield individuals with pink petals in the first filial generation. The red phenotype (and its determining allele) is said to be incompletely dominant over the white phenotype (and its allele). The impact of a gene at the level of the phenotype depends on its dominance relations, but also on the conditions of the rest of the genome and on the conditions of the environment. See also PENETRANCE.

partial dominance (incomplete dominance, semidominance) In genetics, the production of an intermediate phenotype in individuals that are heterozygous for the gene concerned (i.e. the heterozygote shares a phenotype that is quantitatively intermediate between those of the corresponding homozygotes). The impact of a gene at the level of the phenotype depends on its dominance relations, but also on the conditions of the rest of the genome and on the conditions of the environment. See also PENETRANCE.