Genetic Variation Between Human Populations

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Population demographic factors such as age, sex, diet and ethnicity explain the largest proportion of genetic variation between human populations (Fumagalli et al., 2011). Infectious agents including viruses, bacteria and protozoa are likely one of the strongest evolutionary drivers of the remaining genetic diversity within and between populations, as a result of the selective pressure they inflict in regions where infection is endemic. Mortality is the strongest selective pressure which is imposed by an infectious agent. Any genetic variant associated with an improved response to that pathogen is likely to be a target for selection (Fumagalli et al., 2011). Positive selection results in the increased frequency of a beneficial allele. Balancing selection maintains diversity, while negative selection eliminates deleterious variants. This process of natural selection leaves behind distinctive signatures of selection that can be exploited to identify regions of the genome under selection (Karlsson et al., 2014). Signatures of selection are distinctive because they reflect uncommon patterns of allele frequencies at a particular locus when compared to the underlying genetic variation. Candidate based gene approaches, Genome wide association studies (GWAS), haplotype based methods and various statistical tests such as Tajima’s D statistic are used to detect these signatures of selection within the human genome. This essay uses specific examples to discuss the evidence of

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