engleski

Quantifying the increase in human individual genome-wide heterozygosity through isolate break-up and admixture.

Aim. The human population is undergoing a major transition from a metapopulation structure (subdivision in many relatively isolated comunities) to a more admixed structure such as that which occurs in large cities. We attempted to quantify the magnitude of increase in average individual genome-wide geterozygosity (IGWH) that has occured through isolate break-up and admixture. Matherials and methods. We sampled 100 examinees from 9 isolated vilages on 5 Croatian islands, and an additional 101 immigrants into those wilages. Out of the large sample of 1001 examinees, we carefully selected 6 samples each of 23 individuals with a predicted increasing level of genome-wide heterozygosity, which was then measured studied using 1, 200 STR markers. The first sample was from the most isolated island, the second from less isolated island, the third from the least isolated island, the fourth inluded individuals admixed between villages, the fifth immigrants from mainland cities and the sixth extremely outbred indivifuals. Results. Relative to mean IGWH estimate in the first sample, the increase in the percentage of the genome that is heterozygous in the remaining 5 samples was found to be: 2.3%, 3.8%, 5.8%, 6.7% and 7.9%. These differences are statisticaly highly significant (p<0.0001), and their gradual increase follows the predictions based on a priori hypothesis. Conclusion. The human population is undergoing substantial outbreeding through breakup of isolate communities and rural-urban migration, with the potential to increase average genome-wide heterozygosity by up to 10%. The health consequences of this major change in genetic structure merit further study.

isolated populations; genome-wide heterozygosity; Croatian islands

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