A cytogenetic study of Khanty from the lower Ob river in West Siberia has detected a high frequency of the Y chromosome heterochromatin subtotal deletion--del(Y)(q12). This morphologically identical deletion was found in 32 of 154 males examined (20.8%). The carriers had 10 different surnames. Taking into account the small size, isolation by distance, and historical peculiarities of the surname formation of the population, it has been concluded that the high frequency of the del(Y)(q12) results from the genetic drift of the marker chromosome.

При цитогенетическом изучении популяции хантов, проживающих в нижнем течении Оби обнаружена высокая частота распространения субтотальной делеции гетерохроматина Y-хромосомы — del(Y) (q12). Идентичная маркерная хромосома найдена у 32 из 154 обследованных лиц мужского пола, что составляет 20,8%. С учетом относительной малочисленности и изолированности расстоянием этой этнической группы сделано заключение, что причиной высокого распространения del(Y) (q12) может быть генетический дрейф маркерной хромосомы.

C polymorphism of chromosomes 1, 9 and 16 was studied in 447 Mongoloids of Central Asia living under different ecological conditions; two highland (Kirghiz) and three steppe (Kazakh, Mongolian, and Dungan) populations. C band sizes were estimated according to the semiquantitative 5-level method of Patil and Lubs (1977). All the ethnic groups studied showed statistically significant homogeneity in the frequency of C variants. It is suggested that chromosomal C-heterochromatin material has no selective value in the process of human adaptation to extreme high-altitude factors.

A comparative study of frequencies and types of Q-polymorphic variants in seven autosome pairs (3, 4, 13-15, 21, and 22) was performed in three steppe Mongoloid populations of Central Asia (Kazakhs, Dunghans, Mongolians) and three highland Kirghiz populations of Pamir and Tien-Shan. The three steppe Mongoloid populations showed statistically significant homogeneity both in the frequency of Q-polymorphic variants and the distribution of homo- and heteromorphs, with complete agreement of observed frequencies with those theoretically predicted by the law of Hardy-Weinberg. Similar homogeneity was revealed in the three highland Kirghiz populations of Pamir and Tien-Shan. However, comparative analysis of highland and steppe Mongoloids revealed significant differences in the following variables: (1) mean number of Q variants per individual, 2.50 and 3.49 in the highland and steppe populations, respectively; (2) frequency of Q variants in 7 of the 12 autosomes studied; and (3) distribution of homo- and heteromorphs in four autosomal pairs (13-15, 21), with a preponderance of individuals with increased hemomorph (-/-) frequency in highlanders. The following questions are discussed: (1) the possible selective value of chromosomal Q-heterochromatin material in the adaptation of human populations to extreme environmental factors, in particular to the high-altitude environment of Pamir and Tien-Shan; (2) the existence of intraracial heterogeneity in Mongoloids living in different ecological zones; and (3) the possible taxonomic value of Q-variant inversion in chromosome 3.