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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.
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.
Phenotypic plasticity refers to some of the changes in an organism's behavior, morphology and physiology in response to a unique environment. [1] [2] Fundamental to the way in which organisms cope with environmental variation, phenotypic plasticity encompasses all types of environmentally induced changes (e.g. morphological, physiological, behavioural, phenological) that may or may not be ...
Organisms with resource polyphenisms show alternative phenotypes that allow differential use of food or other resources. One example is the western spadefoot toad, which maximizes its reproductive capacity in temporary desert ponds. While the water is at a safe level, the tadpoles develop slowly on a diet of other opportunistic pond inhabitants.
The size of a tomato is one example of a complex trait. Complex traits are phenotypes that are controlled by two or more genes and do not follow Mendel's Law of Dominance. They may have a range of expression which is typically continuous. Both environmental and genetic factors often impact the variation in expression.
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 ...
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.
QTL is a region of a gene that corresponds to a specific phenotypic trait, and the measuring the statistical frequencies of the traits can be helpful in analyzing phenotypic trends. [9] In one study, the analysis showed that directional changes in QTLs affecting various traits were more common than expected by chance among diverse species.