Expressivity

Expressivity refers to variations of a phenotype in genetics. The term is used to qualitatively characterize the variance or extent of the phenotype. For example a quantitative trait - like body height - might have large variance and therefore can make prediction of the phenotype difficult. Like penetrance in most instances expressivity is related to an allele or a mutation or more generally a genotype. In these instances expressivity denotes how well the phenotype can be predicted, given the genotype.