[Polymorphism of the heterochromatic regions of chromosomes 1, 9, 16 and Y and mental retardation].

Polymorphism of the heterochromatic regions (HR) on chromosomes 1, 9, 16 and in three groups of boys at the age of 3 to 14 years was studied. Two groups of boys with olygophrenia of unknown etiology differed by the extent of mental defect, the latter being debility in 50 children, while other 50 children had the profound mental defect. The control group consisted of 50 healthy children.

[Role of non-histone proteins in the transformations and genetic functioning of the chromosome].

The functional relationship between the transformations of chromosome structure and parallel changes of its major components, i. e. DNA, histones and non-histone proteins (NHP) has been analysed.

[Variability of the heterochromatic regions of human chromosomes 1, 9, 16, and Y].

The variability of heterochromatic regions on chromosomes 1, 9, 16 and Y has been studied in a group of unrelated subjects (50 boys and 50 girls) using quantitative methods. Analysis of intercellular (with one subject) variability of chromosome C-segments lengths has shown that their absolute lengths vary considerably with the cell sample examined, while the relative lengths (a part of the total length of C-segment of the chromosomes being studied) are more stable. The relative lengths may be helpful in individual characteristics, reproducible in repeated analysis, which may be used in zygosity testing in twins, family analysis, etc.

[Variability of the C-segment sizes of chromosomes 1, 9, 16 and Y in the human chromosome set].

The investigation of chromosome polymorphism by quantitative methods is a rather hard task. The manual method for measuring C-segments of chromosomes 1, 9, 16 and Y in man is suggested, which is not difficult, being reasonably precise for the population research. Metaphases of the average level of chromosome condensation were taken for analysis.

[Heterochromatin and chromosomal polymorphism].

The structure and sizes of different short deletions of Drosophila melanogaster X-chromosome: left break in the region of locus y-ac-sc, right break in different parts of the heterochromatic region (HR) near the centromere, of the nuclei of salivary glands and metaphases of oogonia were compared. It is suggested, that the development of large blocks of deoxynucleoproteins by a small number of loci of the HR, observed in mitotic chromosomes, is due to their ability to undergo additional replication, as it previously has been shown for locus bobbed. HR in human chromosomes provide high polymorphism of the chromosome sets.

[Spiralization dynamics of the eu- and heterochromatin of heteromorphic homologs of the 1st pair of human chromosomes].

Peculiarities of mitotic spiralization of eu- and heterochromatic parts of heteromorphic homologous chromosomes No 1 are investigated. The homologues differ in size of their centromeric heterochromatin segments. In the spiralization range studied (the total lengths of chromosome pair equal to 8.