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Genetic variability is either the presence of, or the generation of, genetic differences. It is defined as "the formation of individuals differing in genotype , or the presence of genotypically different individuals, in contrast to environmentally induced differences which, as a rule, cause only temporary, nonheritable changes of the phenotype ."
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 ...
Genetic variation Genetic variation of Eurasian populations showing different frequency of West- and East-Eurasian components. [56] It is commonly assumed that early humans left Africa, and thus must have passed through a population bottleneck before their African-Eurasian divergence around 100,000 years ago (ca. 3,000 generations).
Population bottleneck followed by recovery or extinction. A population bottleneck or genetic bottleneck is a sharp reduction in the size of a population due to environmental events such as famines, earthquakes, floods, fires, disease, and droughts; or human activities such as genocide, speciocide, widespread violence or intentional culling.
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.
Genetic drift is a change in allele frequencies caused by random sampling. [40] That is, the alleles in the offspring are a random sample of those in the parents. [41] Genetic drift may cause gene variants to disappear completely, and thereby reduce genetic variability.
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.
Occurrence of this phenomenon not only can result in major phenotypic changes but also reveal the expression of otherwise lethal genetic mutations. [3] Genetic mutations involved in mosaicism may be due to endogenous factors, such as transposons and ploidy changes, or exogenous factors, such as UV radiation and nicotine. [4]
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