Several forms of pathologies, referred to as Yakut hereditary diseases, have been distinguished on the basis of the results of genetic epidemiological studies of Mendelian diseases in the population of the Republic of Sakha (Yakutia): spinocerebellar ataxia type I, myotonic dystrophy, oculopharyngeal muscular dystrophy, hereditary enzymopenic methemoglobinemia, and 3-M syndrome. These diseases are characterized by a high prevalence among Yakuts as compared to their global incidence in the. Data on the molecular nature of mutations in genes responsible for these hereditary diseases are presented.