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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.
Watterson's estimator is commonly used for its simplicity. When its assumptions are met, the estimator is unbiased and the variance of the estimator decreases with increasing sample size or recombination rate. However, the estimator can be biased by population structure.
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]
The allele frequency spectrum can be written as the vector = (,,,,), where is the number of observed sites with derived allele frequency .In this example, the observed allele frequency spectrum is (,,,,), due to four instances of a single observed derived allele at a particular SNP loci, two instances of two derived alleles, and so on.
Biodiversity informatics is the application of informatics techniques to biodiversity information, such as taxonomy, biogeography or ecology.It is defined as the application of Information technology technologies to management, algorithmic exploration, analysis and interpretation of primary data regarding life, particularly at the species level organization. [1]
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.
An SDRF file is a tab-delimited file describing the relationships between samples, arrays, data, and other objects used or produced in a microarray investigation. For simple experimental designs, constructing the SDRF file is straightforward, and even complex loop designs can be expressed in this format.
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.