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.