“…In two cities of the region, Karachaevsk and Cherkessk, representatives of these groups live together, but in the rural districts, ethnoses are largely isolated from each other. Monoethnic marriages between Karachays, according to epidemiological studies, account for 88.3% of marriages [ 7 ]. In a small population, this situation can decrease genetic variability and change the frequency of homozygotes in the population; in particular, an increase in the frequencies of specific nosological forms is possible.…”