Возможно ли что из за делеции которую можно назвать вредной, у Славян был демографический взрыв?
Genetic reproductive edge may have boosted Slavic expansions
Open access at PLoS ONE:
The vast majority of patients with Nijmegen Breakage Syndrome (NBS) are of Slavic origin and carry a deleterious deletion (c.657del5; rs587776650) in the NBN gene on chromosome 8q21. This mutation is essentially confined to Slavic populations and may thus be considered a Slavic founder mutation. Notably, not a single parenthood of a homozygous c.657del5 carrier has been reported to date, while heterozygous carriers do reproduce but have an increased cancer risk. These observations seem to conflict with the considerable carrier frequency of c.657del5 of 0.5% to 1% as observed in different Slavic populations because deleterious mutations would be eliminated quite rapidly by purifying selection. Therefore, we propose that heterozygous c.657del5 carriers have increased reproductive success, i.e., that the mutation confers heterozygote advantage. In fact, in our cohort study of the reproductive history of 24 NBS pedigrees from the Czech Republic, we observed that female carriers gave birth to more children on average than female non-carriers, while no such reproductive differences were observed for males. We also estimate that c.657del5 likely occurred less than 300 generations ago, thus supporting the view that the original mutation predated the historic split and subsequent spread of the ‘Slavic people’. We surmise that the higher fertility of female c.657del5 carriers reflects a lower miscarriage rate in these women, thereby reflecting the role of the NBN gene product, nibrin, in the repair of DNA double strand breaks and their processing in immune gene rearrangements, telomere maintenance, and meiotic recombination, akin to the previously described role of the DNA repair genes BRCA1 and BRCA2.
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Of the 92 haplotypes that carried NBN c.657del5 and that could be deduced without ambiguity (S1 File), 22 (23.9%) carried identical alleles at all markers between the two most distant microsatellites D8S271 (allele 257) and D8S270 (allele 200). This haplotype (Table
was found in individuals from Poland, Germany, CS [Czech Republic/Slovakia] and Lusatia (Sorbs) and most likely represents the ancestral haplotype. The remaining 95 haplotypes from 40 homozygous and 15 heterozygous c.657del5 carriers (out of a total of 187 chromosomes) could not be resolved without ambiguity and are best guesses (S1 File). Among these haplotypes, we observed the putative ancestral haplotype not only in individuals from the countries mentioned above, but also from Bulgaria, Russia, and the Ukraine. Some 30% of chromosomes carrying the founder mutation showed the deduced founder haplotype (Table
. Moreover, all 187 chromosomes carrying c.657del5 showed the same SNP alleles (Table 3). Therefore, the deletion is not only confined to individuals of Slavic origin but is most likely due to a single mutational event. All differences observed for individual microsatellite alleles are explicable by past recombination or mutation owing to the non-negligible recombination rate between the STR markers (Table 2) and the high mutation rates of microsatellites of 10−4 to 10−2 per generation.
Seemanova E, Varon R, Vejvalka J, Jarolim P, Seeman P, Chrzanowska KH, et al. (2016) The Slavic NBN Founder Mutation: A Role for Reproductive Fitness? PLoS ONE 11(12): e0167984. doi:10.1371/journal.pone.0167984
Тема: Генетические маркеры и заболевания (Прочитано 17299 раз)