Genetic distance
Encyclopedia
Genetic distance refers to the genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 divergence between species or between populations within a species. It is measured by a variety of parameters. Smaller genetic distances indicate a close genetic relationship whereas large genetic distances indicate a more distant genetic relationship. Genetic distance can be used to compare the genetic similarity between different species, such as humans and chimpanzees. Within a species genetic distance can be used to measure the divergence between different sub-species.

In its simplest form, the genetic distance between two populations is the difference in frequencies of a trait. For example the frequency of RH
RH
RH, Rh, rH, or rh can stand for:* Riemann hypothesis, an important unsolved problem in mathematics* Ryan's Hope, a soap opera* Rhesus factor, a classification to describe blood types in humans* Rhodium, a chemical element...

 negative individuals is 50.4% among Basques, 41.2% in France and 41.1% in England. Thus the genetic difference between the Basques and French is 9.2% and the genetic difference between the French and the English is 0.1% for the RH negative trait.
The genetic distance of several individual traits can then be averaged to compute an overall genetic distance.

Measures of genetic distance

There are several measures used to indicate genetic distance. These include:

Fixation index

A commonly used measure of genetic distance is the fixation index which varies between 0 and 1. A value of 0 indicates that two populations are genetically identical whereas a value of 1 indicates that two populations are different species.

Nei's standard genetic distance

This measure assumes that genetic differences arise due to mutations and genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...

.

Cavalli-Sforza and Edwards 1967

This measure assumes that genetic differences arise due to genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...

 only.

Reynolds, Weir, and Cockerham's 1983

This measure assumes that genetic differences arise due to genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...

only.

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