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Tajima's D is a population genetic test statistic created by and named after the Japanese researcher Fumio Tajima. [1] Tajima's D is computed as the difference between two measures of genetic diversity: the mean number of pairwise differences and the number of segregating sites, each scaled so that they are expected to be the same in a neutrally evolving population of constant size.
Evolution is the change in the heritable characteristics of biological populations over successive generations. [1] [2] It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. [3]
Through natural selection and random genetic drift, the traits with a negative effect on population fitness disappear from the gene pool. The balance between the influence of natural selection and genetic drift on the population mutation rate is mainly determined by the population size. [5]
This process is often characterized by a description of the starting and ending states, or the kind of change that has happened at the level of DNA (e.g,. a T-to-C mutation, a 1-bp deletion), of genes or proteins (e.g., a null mutation, a loss-of-function mutation), or at a higher phenotypic level (e.g., red-eye mutation).
Genetic variation is the difference in DNA among individuals [1] or the differences between populations among the same species. [2] The multiple sources of genetic variation include mutation and genetic recombination. [3] Mutations are the ultimate sources of genetic variation, but other mechanisms, such as genetic drift, contribute to it, as ...
A mutation will increase genetic diversity in the short term, as a new gene is introduced to the gene pool. However, the persistence of this gene is dependent of drift and selection (see above). Most new mutations either have a neutral or negative effect on fitness, while some have a positive effect. [11]
A coherent theory of neutral evolution was first proposed by Motoo Kimura in 1968 [9] and by King and Jukes independently in 1969. [10] Kimura initially focused on differences among species; King and Jukes focused on differences within species. Many molecular biologists and population geneticists also contributed to the development of the ...
They seek answers to questions such as which genes are involved, how interdependent are the effects of different genes, what do the genes do, and what changes happen to them (e.g., point mutations vs. gene duplication or even genome duplication).