Normal polymorphism of the (CTG)(n) repeat in the myotonin protein kinase (DM) gene on chromosome 19q13.3 in Eastern European populations

Polymorphism of a highly polymorphic CTG repeat in the 3'-untranslated regi on of the myotonin protein kinase gene was analyzed in healthy people from several Eastern European populations (Russians, Moldovans, Belarussians, Ko mis, Chuvashes, Udmurts, Bashkirs, Tatars, Maris, and Mordovians). In total , 26 alleles of the CTG repeat were found, the repeat number ranging from 5 to 33 (alleles with six and seven repeats were not detected). The heterozy gosity of individual populations varied from 61 to 91%. In the total sample combining all populations, the observed and expected heterozygosities did not differ (fixation index -0.0022), suggesting selective neutrality of the normal polymorphism of the CTG repeat in the myotonin protein kinase gene.