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The variation ratio is a simple measure of statistical dispersion in nominal distributions; it is the simplest measure of qualitative variation. It is defined as the proportion of cases which are not in the mode category:
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]
V P = V E + V G, where the terms refer to variation in phenotype, environment, and genotype respectively. [1] Broad sense heritability (H 2, or H B) refers to the phenotypic differences arising from all genetic effects, and can be described as the ratio of genotypic variation to that of phenotypic variation in the population, or: H 2 = V G / V P.
Genetic variation can be identified at many levels. Identifying genetic variation is possible from observations of phenotypic variation in either quantitative traits (traits that vary continuously and are coded for by many genes, e.g., leg length in dogs) or discrete traits (traits that fall into discrete categories and are coded for by one or a few genes, e.g., white, pink, or red petal color ...
Heritability increases when genetics are contributing more variation or because non-genetic factors are contributing less variation; what matters is the relative contribution. Heritability is specific to a particular population in a particular environment.
Nucleotide diversity is a measure of genetic variation. It is usually associated with other statistical measures of population diversity, and is similar to expected heterozygosity . This statistic may be used to monitor diversity within or between ecological populations, to examine the genetic variation in crops and related species, [ 3 ] or to ...
This variation in expression can be affected by modifier genes, epigenetic factors or the environment. [3] Modifier genes can alter the expression of other genes in either an additive or multiplicative way. [3] Meaning the phenotype that is observed can be a result of two different alleles (gene variants) being summed or multiplied.
Fisher's principle is an evolutionary model that explains why the sex ratio of most species that produce offspring through sexual reproduction is approximately 1:1 between males and females. A. W. F. Edwards has remarked that it is "probably the most celebrated argument in evolutionary biology". [1]