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Genetic distance
Genetic distance is a measure of the genetic divergence between species or between populations within a species. Populations with many similar alleles have small genetic distances. This indicates that they are closely related and have a recent common ancestor.
Genetic distance is useful for reconstructing the history of populations. For example, evidence from genetic distance suggests that African and Eurasian people diverged about 100,000 years ago. Genetic distance is also used for understanding the origin of biodiversity. For example, the genetic distances between different breeds of domesticated animals are often investigated in order to determine which breeds should be protected to maintain genetic diversity.〔Ruane, J. (1999). A critical review of the value of genetic distance studies in conservation of animal genetic resources. Journal of Animal Breeding and Genetics, 116(5), 317-323. Chicago.〕
==Biological foundation==
In the genome of an organism, each gene is located at a specific place called the locus for that gene. Allelic variations at these loci cause phenotypic variation within species (e.g. hair colour, eye colour). However, most alleles do not have an observable impact on the phenotype. Within a population new alleles generated by mutation either die out or spread throughout the population. When a population is split into different isolated populations (by either geographical or ecological factors), mutations that occur after the split will be present only in the isolated population. Random fluctuation of allele frequencies also produces genetic differentiation between populations. This process is known as genetic drift. By examining the differences between allele frequencies between the populations and computing genetic distance, we can estimate how long ago the two populations were separated.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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