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Examples of human phenotypic variability: people with different levels of skin colors, a normal distribution of IQ scores, the tallest recorded man in history - Robert Wadlow - with his father. Human variability, or human variation, is the range of possible values for any characteristic, physical or mental, of human beings.
Ronald Fisher in 1913. Genetic variance is a concept outlined by the English biologist and statistician Ronald Fisher in his fundamental theorem of natural selection.In his 1930 book The Genetical Theory of Natural Selection, Fisher postulates that the rate of change of biological fitness can be calculated by the genetic variance of the fitness itself. [1]
Phenotypic variation (due to underlying heritable genetic variation) is a fundamental prerequisite for evolution by natural selection. It is the living organism as a whole that contributes (or not) to the next generation, so natural selection affects the genetic structure of a population indirectly via the contribution of phenotypes.
Environmental factors and other external influences can also play a role in phenotypic variation. Genetic architecture is a broad term that can be described for any given individual based on information regarding gene and allele number, the distribution of allelic and mutational effects, and patterns of pleiotropy , dominance , and epistasis .
Environmental variance can be explicitly modeled by studying individuals across a broad range of environments, although inference of genetic variance from phenotypic and environmental variance may lead to underestimation of heritability due to the challenge of capturing the full range of environmental influence affecting a trait.
Three different types of genetic selection. On each graph, the x-axis variable is the type of phenotypic trait and the y-axis variable is the amount of organisms. Group A is the original population and Group B is the population after selection. Top (Graph 1) represents directional selection with one extreme favored.
The heritability of a trait is the proportion of the total (phenotypic) variance (σ 2 P) that is attributable to genetic variance, whether it be the full genotypic variance, or some component of it. It quantifies the degree to which phenotypic variability is due to genetics: but the precise meaning depends upon which genetical variance ...
This classic behaviour genetic model aims to partition the phenotypic variance into three categories: additive genetic variance (A), common (or shared) environmental ...