Epistasis

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Related to Epistatic Gene: modifier genes

epistasis

[ə′pis·tə·səs]
(genetics)
The suppression of the effect of one gene by another.
(medicine)
A checking or stoppage of a hemorrhage or other discharge.
(pathology)
A scum or film of substance floating on the surface of urine.

Epistasis

 

the interaction of two nonallelic genes (that is, genes that are at different loci) whereby one of them, called the epistatic gene, suppresses the effect of the other one, called the hypostatic gene. Phenotypically, epistasis is manifested as a deviation from the segregation that would be expected in digenetic inheritance; in this case, however, there is no violation of Mendel’s laws, inasmuch as the alleles of the interacting genes are distributed in complete conformity to the law of independent assortment, or combination.

References in periodicals archive ?
Many of the useful human selection traits in inbred development are expressed by additive, dominant, or epistatic gene action in hybrids.
Here, transition matrix simulation is used to explore selection response under additive versus additive x additive epistatic gene action and examine the differences between these models in magnitude and longevity of selection response.
If favorable epistatic effects exist between loci in Parent 1 or between loci in Parent 2, and they are different sets of epistatic genes in the two parents, then one might expect the average of backcross populations to be superior to the [F.
Commercial maize breeding as commonly conducted is effective in selecting favorable epistatic gene combinations.
Gradual breaking of close linkages and forming of new epistatic gene combinations presumably ensures gains during many breeding cycles.
With current procedures, however, reciprocal chromosome substitution lines and reciprocal recombinant chromosome lines can be used to only determine additive or epistatic gene action because the lines are homozygous.
Furthermore, molecular markers show similarities among individuals by site sampling, while morphological characteristics measure how equal the individuals are according to variables whose expression levels depend on the number of potentially epistatic genes (GRIVET; NOYER, 2003).
However, the most broadly supported theory suggests a polygenic mode of inheritance with epistatic genes, stochastic developmental events and environmental factors exerting some influence on the phenotypic expression of the genes involved [Theslef, 2000].
The actual effects of the epistatic genes often vary from the example just given, but the general control of such genes is predictable within any genetic system studied.
If Sewall Wright's shifting balance theory is plausible, then complex characters will be controlled by epistatic genes and influenced by other nonlinear components of the genetic system.