Human chromosomal polymorphism. VII. The distribution of chromosomal Q-polymorphic bands in different human...

The distribution of chromosomal Q-polymorphic bands was studied in different human populations. The populations studied showed no differences in the relative amount of Q bands in all the 12 polymorphic loci of seven autosomes, but interpopulation differences did exist in the absolute amount of Q bands in all the 12 potentially polymorphic loci of seven autosomes, these differences consisting of uniform increases or decreases in this absolute amount. Comparisons of the mean number of Q-heterochromatin bands with fluorescence levels 4 and 5 per individual showed a consistent prevalence of this quantitative parameter of chromosomal Q polymorphism in females as compared to males in all the national groups. It is suggested that there is some dosage compensation of chromosomal Q-heterochromatin material in females due to the absence of a chromosome in their genome, which is able to "compensate" for the large Q band in chromosome Y which is present only in the karyotype of males.