Genetic distance
Genetic distance refers to the genetic 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 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.[1]
Contents |
Measures of genetic distance [edit]
There are several measures used to indicate genetic distance.[2] These include:
Fixation index [edit]
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 [edit]
This measure assumes that genetic differences arise due to mutations and genetic drift.[3]
Cavalli-Sforza and Edwards 1967 [edit]
This measure assumes that genetic differences arise due to genetic drift only. only ∇
Reynolds, Weir, and Cockerham's 1983 [edit]
This measure assumes that genetic differences arise due to genetic drift only.
See also [edit]
References [edit]
- ^ Cavalli-Sforza, L. L. Genes, Peoples, and Languages. Berkeley: University of California Press, 2001. ISBN 0-520-22873-1 ]
- ^ Population Genetics IV: Genetic distances -- biological vs. geometric approaches.
- ^ Nei, Masatoshi (1973). "SAMPLING VARIANCES OF HETEROZYGOSITY AND GENETIC DISTANCE". Genetics.
External links [edit]
- The Estimation of Genetic Distance and Population Substructure from Microsatellite allele frequency data., Brent W. Murray (May 1996), McMaster University website on genetic distance
- Computing distance by stepwise genetic distance model, web pages of Bruce Walsh at the Department of Ecology and Evolutionary Biology at the University of Arizona
- Britten RJ. Divergence between samples of chimpanzee and human DNA sequences is 5%, counting indels. PNAS; 2002:13633
 |
This evolution-related article is a stub. You can help Wikipedia by expanding it. |
 |
This genetics article is a stub. You can help Wikipedia by expanding it. |
