Expressivity 1732638 194209519 2008-02-26T17:55:31Z SmackBot 433328 Date the maintenance tags or general fixes {{Wikify|date=February 2008}} {{Unreferenced|date=February 2008}} '''Expressivity''' is a term used in [[genetics]] that refers to variations of a [[phenotype]] in individuals carrying a particular [[genotype]]. The term can be used to qualitatively or quantitatively characterize the extent of the phenotype variation given a particular genotype. The term is equivalent to the severity of a condition in clinical medicine. For example, the amount of blood ejected from the pumping heart with each contraction can be quantitated by echocardiography and is called the ejection fraction. If a specific genotype is associated with the development of congestive heart failure, the expressivity would be represented by the range of ejection fractions seen in patients that have that genotype. As a more qualitative example, the "blue" gene might have an expressivity of 25% for individuals that express the "blue" gene and appear light blue, and 75% for individuals that express the "blue" gene and appear dark blue. This differs from [[penetrance]] in that penetrance refers to the likelihood of the gene generating any phenotype at all, while expressivity refers to the influence of an expressed gene in individuals. ''Variable expressivity'' occurs when a phenotype is expressed to a different degree among individuals with the same genotype. For example, individuals with the same allele for gene involved in a quantitative trait like body height might have large variance (some are taller than others), making prediction of the phenotype from a particular genotype alone difficult. The expression of a phenotype may be modified by the effects of aging, other genetic loci or environmental factors. ==See also== *[[Penetrance]] *[[Allele]] *[[Phenotype]] *[[Genotype]] *[[Mendelian inheritance]] {{genetics-stub}} [[Category:Population genetics]] [[cs:Expresivita genu]] [[de:Expressivität]] [[zh:表现度]]