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Related to Penetrance: expressivity, Incomplete penetrance


The proportion of individuals carrying a dominant gene in the heterozygous condition or a recessive gene in the homozygous condition in which the specific phenotypic effect is apparent. Also known as gene penetrance.



a quantitative index of phenotypic variability in the expression of a gene. Penetrance is usually measured as the percent ratio of the number of individuals in whom the gene is expressed to the total number of individuals in whose genotype the gene is present in the homozygous state (for recessive genes) or heterozygous state (for dominant genes). Complete penetrance occurs when a certain gene is expressed in 100 percent of individuals with the appropriate genotype. Penetrance can also be incomplete, in which case it is called variable.

Variable penetrance is characteristic of the expressivity of many genes in humans, animals, plants, and microorganisms. For example, certain hereditary diseases of man develop only in a portion of the persons whose genotype contains the anomalous gene; in the remainder, the hereditary predisposition to the disease remains unrealized. Variable penetrance is due to the complexity and multistage nature of the many events that occur between the first actions of a gene on the molecular level and the eventual emergence of a trait. The penetrance of a gene may vary within broad limits, depending on the nature of the surrounding genes within the genotype. Strains of individuals with a given degree of penetrance may be obtained by artificial selection. The average degree of penetrance also depends on environmental conditions.


Lobashev, M. E. Genetika, 2nd ed. Leningrad, 1967.
Timofeev-Resovskii, N. V., and V. I. Ivanov. “Nekotorye voprosy fenogenetiki.” In the collection Aktual’nye voprosy sovremennoi genetiki. Moscow, 1966. Pages 114–30.


References in periodicals archive ?
1) Other family members were not involved in this case and it might be due to autosomal recessive inheritance or incomplete penetrance and variable expression in parents.
Hereditary retinoblastoma shows autosomal dominant inheritance with 90% clinical penetrance.
2 This is an autosomal dominant disorder with less penetrance in men so mainly expressed in females.
The inheritance of TSC is an autosomal dominant trait with variable penetrance.
Expression looks at individual phenotypes, while penetrance is population-wide.
This suggests that the mutation was inherited from the mother and not the father The sequencing of UBQLN2-S3401 in this case indicated the presence of an X-linked ALS/FTD with incomplete penetrance in this family (Figure l).
Annotations at the gene level include, but are not limited to, transcript isoform, associated phenotype, major inheritance pattern, disease penetrance and prevalence if known, clinical sensitivity, and attributable risk (a measure of allelic and locus heterogeneity of the gene and disorder).
Penetrance and variability in malformation syndromes.
2) The increasing use of next-generation sequencing (which yields information on moderate- and low- penetrance genes in addition to BRCA status) means that women and their providers increasingly are being confronted with genetic testing results that call for formal genetics expertise.
ERT is now well established in the treatment of Fabry disease; however, there still remains concern about its efficacy, tissue penetrance, and intravenous administration.
Moreover, even when a known molecular defect can be identified, interpretation of this finding is complicated by compound mutations and variable penetrance even among members of the same family who share a mutation.