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the percentage of individuals of a specific genotype that express an expected phenotype
Source: Jenkins, John B. 1990. Human Genetics, 2nd Edition. New York: Harper & Row ...

Penetrance: The percentage of individuals in a population that actually exhibit the (mutant) phenotype even though they carry the mutation ...

In genetics, the proportion of individuals with a particular genotype that show the phenotype ascribed to that genotype.
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penetrance /PEN-ə-trəns/ The probability of a genotype being expressed. When penetrance is complete, the genotype is expressed in all individuals who have that genotype.

Penetrance Pertaining to the failure of some animals with a mutant genotype to express the associated mutant phenotype.

The probability of a gene or genetic trait being expressed. "Complete" penetrance means the gene or genes for a trait are expressed in all the population who have the genes.

The influence of other, unidentified factors can be seen when some individuals in a study do not display the phenotype normally associated with their defined genotype, a situation termed nonpenetrance.

Term coined by Voigt (1926) for the percentage with which a dominant or homozygous recessive gene expresses itself in the phenotype. Qualitative concept of gene expression. It depends both on genotype and environment.

Table 1. Penetrance of phenotypes in Ptdsr -/- mice from E9.5 to E18.5, as detected by gross morphology
Expression of Ptdsr during embryogenesis and in adult tissues ...

Penetrance An "ll or none" reference to clinical expression of a mutant gene.
Phage A virus for which the natural host is a bacterial cell.
Physical map A map of the locations of identifiable landmarks on DNA (e.g.

resulting from a given genotype (cystic fibrosis, for example, may have a variable degree of severity). This is different from pleiotropy which refers to a variety of different phenotypes resulting from the same genotype, or from penetrance.

The term is typically used to describe heterozygotes for mutations that cause recessive disease, but it is also used to describe heterozygotes for risk alleles of complex traits with variable penetrance, regardless of inheritance type.

Is there variable expressivity and/or incomplete penetrance?
Is there a clear and accurate legend?
Are the symbols used correctly? Are unknown phenotypes indicated?

In the case of hemochromatosis, penetrance is incomplete, even for the classic HFE mutation, and is affected by gender, diet, and behaviors such as alcohol consumption.

Marfan's Syndrome is associated with incomplete penetrance, therefore not all persons carrying the mutation develop the disease.

Successful identification of behavioral genes is most likely when the gene shows a high penetrance, that is, the genotype is expressed in the phenotype. Degree of expression is also important for success in determining behavioral genes.

Incomplete penetrance -- the gene for a condition is present, but not obviously expressed in all individuals in a family with the gene.

See also: See also: Gene, Mutation, Human, Organ, Environment

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