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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.
Comparing the value of the Watterson's estimator, to nucleotide diversity is the basis of Tajima's D which allows inference of the evolutionary regime of a given locus.
For example it is used to calculate the Tajima's D neutral evolution statistic. A sequence alignment, produced by ClustalO, of mammalian histone proteins. Sequences are the amino acids for residues 120-180 of the proteins. Residues that are conserved across all sequences are highlighted in grey.
Fumio Tajima was born in Ōkawa, in Japan's Fukuoka prefecture, in 1951. [1] [2] He graduated from high school in 1970, completed his undergraduate degree at Kyushu University in 1976, and received a Master's degree from the same institution in 1978. [3]
A number of different Markov models of DNA sequence evolution have been proposed. [1] These substitution models differ in terms of the parameters used to describe the rates at which one nucleotide replaces another during evolution.
Fay and Wu's H is a statistical test created by and named after two researchers Justin Fay and Chung-I Wu. [1] The purpose of the test is to distinguish between a DNA sequence evolving randomly ("neutrally") and one evolving under positive selection.
Tajima's D is based on the expectation that S = theta * x where x is the sum of 1/i for i from 1 to N. Thus, we turn this into a method to estimate theta by noting that theta = E(S)/x. The current version suggests that S/x part is a "normalized" version of segregating sites, and this leads to a mistake in the calculation of D in the example.
George William Hart (born 1955) [1] is an American sculptor and geometer. Before retiring, he was an associate professor of Electrical Engineering at Columbia University in New York City and then an interdepartmental research professor at Stony Brook University .