penetrance

penetrance

 [pen´ĕ-trans]

the frequency with which a heritable trait is manifested by individuals carrying the principal gene or genes conditioning it.

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

pen·e·trance

(pen'ĕ-trans),

The frequency, expressed as a fraction or percentage, of people who are phenotypically affected, among those of an appropriate genotype (i.e., homozygous or hemizygous for recessives, heterozygous or hemizygous for dominants); for an autosomal dominant disorder, if only a proportion of people carrying the mutant allele display the abnormal phenotype, the trait is said to show incomplete penetrance. If all with the mutant allele show the abnormal phenotype, the trait is said to have complete or full penetrance. See: penetration.

Farlex Partner Medical Dictionary © Farlex 2012

penetrance

(pĕn′ĭ-trəns)

n.

The frequency, under given environmental conditions, with which a specific phenotype is expressed by those individuals with a specific genotype.

The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.

penetrance

Penetration The disruption of a surface, as in penetrating–eg, gunshot wounds, hospital-acquired penetration contact due to infected 'sharps', or forcible penetration in rape

McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.

pen·e·trance

(pen'ĕ-trăns)

The frequency, expressed as a fraction or percentage, of people who are phenotypically affected, among people of an appropriate genotype; factors affecting expression may be environmental, or due to purely random variation; contrasted with hypostasis where the condition has a genetic origin and therefore tends to cause correlation in relatives.

Medical Dictionary for the Health Professions and Nursing © Farlex 2012

penetrance

The frequency with which a GENE manifests its effect. Failure to do so may result from the modifying effect of other genes or from environmental influences. A single hereditable dominant or recessive characteristic is either penetrant or not. Penetrance is measured as the proportion of individuals in a population with a particular genotype who show the corresponding PHENOTYPE.

Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

penetrance

the percentage of individuals with a particular GENOTYPE that display the genotype in the PHENOTYPE. For example, a dominant gene for baldness is 100% penetrant in males and 0% penetrant in most females, because the gene requires high levels of the male hormone for expression, an example of SEX LIMITATION. Once a gene shows penetrance it may show a range of EXPRESSIVITY of phenotype.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

penetrance 

The frequency with which the characteristics transmitted by a gene appear in individuals possessing it. Penetrance is represented as the ratio of individuals who carry the gene and express its effects, over the total number of carriers of the gene in a population. Few of the genes in the genome show a high penetrance because environmental factors play a role in development. Examples: familial exudative vitreoretinopathy and neurofibromatosis (type 1 and type 2), which are both inherited as autosomal dominant, have 100% penetrance; about 90% of the children who carry the retinoblastoma gene develop the disease while the gene remains non-penetrant in the remaining 10% of the children. See expressivity; familial exudative vitreoretinopathy.

Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann