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Polygenic adaptation describes a process in which a population adapts through small changes in allele frequencies at hundreds or thousands of loci. [ 1 ] Many traits in humans and other species are highly polygenic , i.e., affected by standing genetic variation at hundreds or thousands of loci.
Complex traits are also known as polygenic traits and multigenic traits. [1] [2] The existence of complex traits, which are far more common than Mendelian traits, represented a significant challenge to the acceptance of Mendel's work. Modern understanding has 3 categories of complex traits: quantitative, meristic, and threshold.
Pleiotropy seems limited for many traits in humans since the SNP overlap, as measured by variance accounted for, between many polygenic predictors is small. Most genetic traits are polygenic in nature: controlled by many genetic variants, each of small effect. These genetic variants can reside in protein coding or non-coding regions of the genome.
Unlike monogenic traits, polygenic traits do not follow patterns of Mendelian inheritance (discrete categories). Instead, their phenotypes typically vary along a continuous gradient depicted by a bell curve. [8] An example of a polygenic trait is human skin color variation.
Complex traits in particular are more likely to have a polygenic basis. [18] Advances in genetic technology have allowed scientists to more closely investigate the genetic basis of complex traits, leading to an accumulation of evidence supporting the importance of polygenic control in understanding the evolution of these traits.
With these traits as being by-products of others it can ultimately be said that these traits evolved but not that they necessarily represent adaptations. Polygenic traits are controlled by a number of separate genes. Many traits are polygenic, for example human height. To drastically change a polygenic trait is likely to require multiple changes.
Traits controlled by two or more genes are said to be polygenic traits. Polygenic means "many genes" are necessary for the organism to develop the trait. For example, at least three genes are involved in making the reddish-brown pigment in the eyes of fruit flies. Polygenic traits often show a wide range of phenotypes.
Phenotypes (measurable traits), such as height or risk for heart disease, are the product of some combination of genes and environment. These traits can be estimated using polygenic scores, which seek to isolate and estimate the contribution of genetics to a trait by summing the effects of many individual genetic variants. To construct a score ...