Genetic variation source

Genetic drift is alteration of allele frequencies in small populations by chance events. During times when large populations are reduced to small numbers of individuals, genetic variation is likely to be lost by chance. Genetic drift also occurs when a small number of individuals colonize a new region. The pioneers are unlikely to have all the alleles found in the source population and the frequencies of the ones they do have are likely to differ from those in the source population. 

Genetic variation of pathogenic agents in microorganism-caused disorders can be an additional source of individual drug sensibility. Since this article only focuses on human polymorphisms, we will illustrate this concept with one example. 

It is also important to understand the source and significance of genetic variations. The Pima Indians have the highest rates of diabetes in the world Tay-Sachs disease is primarily found in Ashkenazi Jews. Contemporary literature indicates that these differences stem from reproductive isolation, not race. Genetic traits common to persons with sickle-cell disease are related to malaria frequency and not our social view of race. This is why the disease can be found in high frequency in Yemen, West Africa, Greece, and Saudi Arabia. 

Source Coronini R, et al. Decoding the literature on genetic variation, Nature Biotechnology 21 21-29 (2003). 

Mutation, discussed previously, is ultimately the source of all new genetic variation in populations. In general, mutation rates do not differ very much from population to population. 

Tautz, D., Trick, M. and Dover, G.A. (1 986) Cryptic simplicity in DNA is a major source of genetic variation. Nature 322, 652-656. 

Post-translational modifications were recognized as additional sources of the structural modification of proteins.(22) Should such a modification occur by an enzyme-mediated process, as had been established for oxidation of sulfhydryl groups or the addition of carbohydrate or phosphate groups, or by the cleavage of the polypeptide with loss of a terminal amino group, or a larger part of the chain, it too could be subject to genetic variation. 

Two questions may be asked at the outset. Which plant species are damaged by air pollution Are there sources of genetic variation available in these species ... 

Horvitz 1989, Hairston Dillon 1990) are important sources of genetic variation. This sort of variation would be expected to increase genetic correlations, in contrast to the optimal-world case. Some believe that laboratory studies of field-evolved populations are therefore biased toward rejecting the optimal-world scenario and are not relevant to the question (Service Rose 1985). 

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