[Chromosome aberrations, chromatin diminution and their significance in understanding the molecular genetic organization of eukaryotic chromosomes]. / Aberratsii khromosom, diminutsiia khromatina i ikh znachenie v ponimanii molekuliarno-geneticheskoi organizatsii khromosom éukariot.

The paper analyzes the significance of new data obtained in the study of mechanism of formation of radiation-induced chromosome aberrations and in the investigation of chromatin diminution for understanding of the principles of the molecular genetical organization of eucaryotic chromosome. It is concluded that the structure of eucaryotic chromosome follows a certain plan. For its formation, a large number of various innovations were necessary, which could not been prepared simultaneously under the directed action of natural selection based upon the stochastic mutation process.

[The G1-process in human lymphocytes cultured with PHA, and formation of radiation-induced chromosome aberrations]. / G1-protsess v limfotsitakh cheloveka, kul'tiviruemykh s FGA, i obrazovanie radiatsionno-indutsirovannykh aberratsii khromosom.

Experimental evidence for the existence of local spontaneous DNA synthesis in PHA-stimulated human lymphocytes at the G1 phase (G1 process) is presented. This process is associated with the appearance of single-stranded DNA breaks and their subsequent reparation. DNA sequences involved in the G1 process were characterized in terms of their nucleotide composition and association with the nuclear matrix. It was shown that the G1 process occurs in chromosome regions in which radiation-induced exchange-type chromosome aberrations arise. The results of the study are regarded as evidence in favor of a molecular version of the primary contact theory of chromosomal mutagenesis. A possible role of G1 process disturbances in pathogenesis of chromosome instability syndromes in humans is discussed.

[Mutagenesis and genetic homeostasis in higher organisms]. / Mutagenez i geneticheskii gomeostaz u vysshikh organizmov.

Structural genes and genetic regulatory sites occupy merely a small space in the eukaryotic genome; the remaining space presents various uncoding sequences. Genomic reorganizations, i.e. changes in the mutual arrangements of nucleotide sequences in DNA, appearance of new sequences and disappearance of old ones, have occurred in evolution many times. The genomic reorganizations reflect biological mutagenesis which cannot basically depend on primary DNA damages. Ionizing radiation and traditional chemical mutagens are unable to induce great genomic reorganizations. The cellular genetic apparatus alone plays a key role in maintaining genetic homeostasis and preventing genomic reorganizations. There are some examples of genomic reorganizations in eukaryotes, including those resulting in human hereditary diseases. There are evidence for that chromosomal aberrations occur in the minor site of a genome, which is topologically related to the nuclear matrix.

[Cytogenetic effect of the radiosensitizing action of 5-bromo-2'-deoxyuridine on eukaryotic cells at various periods of the DNA synthesis phase]. / Tsitogeneticheskii éffekt radiosensibiliziruiushchego deistviia 5-brom-2'-dezoksiuridina na kletki éukariot v otdel'nykh otrezkakh fazy sinteza DNK.

The effect of 5-bromo-2'-deoxyuridine (BUDR) radiosensitizing action on meristematic cells of wheat seedlings and human peripheral blood lymphocytes synchronized with 5-fluoro-2'-deoxyuridine at the G1-S boundary was revealed. This effect was only found in the beginning of the S phase. We show that it was conditioned by incorporation of BUDR into special early replicating DNA sequences which are specific for chromosomal mutagenesis. Using the molecular biology methods non-random distribution of 3H-BUDR in the early replicating wheat DNA sequences with different degree of repeating was found.