A Study on Damage of Chromosomes Activity in Seedlings of Crepis Capillaris - Progress in Organic and Physical Chemistry: Structures and Mechanisms - page 262

The study of chemical mutagens is a large role belongs to works of J. A. Rapoport
[3]. He is discoverer of the chemical mutagenesis. He revealed out su-
permutagens and discovered of possibilities their application in the breeding of crops
and in other areas of agricultural production. J. A. Rapoport organized synthesis of su-
permutagens. Every year, he organized since 1959 the All-Union Conferences for Sci-
entists and Breeders on chemical mutagenesis and its application in agriculture. These
meetings served in those years a good genetic school, especially for young breeders,
who were trained and the unscienti¿ c method of Lysenko. Based on the methodology
developed by Rapoport and with the help of mutagens, which he distributed free of
charge, breeders created the source material of crops and introduced new varieties [3].
A series of investigations on the application of the chemical mutagen ethyleneimine
and mechanism of its action in winter wheat was conducted and is ongoing, N. S. Ei-
ges [6, 7], which is the of J. A. Rapoport.
The most effective and affordable way to analyze the mutagenesis is a cytogenetic
method: the study of rearrangements (aberrations) of chromosomes observed in divid-
ing cells (mitosis and ), and disorders in passing of the mitotic cycle.
The mechanism damage of the chromosomes and their relationship to the mitotic
cycle and synthesis DNA at various biological objects in the cells of the meristem of
plants onions, Vicia faba , Crepis , and so on, embryonic cells of animals and humans
in vitro , at microbes, viruses, and other objects.
The ionizing radiation damages the chromosomes immediately after irradiation at
all stages of the mitotic cycle “undelayed” effect. In the cells that came into mitosis
from G 2 phase and S, arise aberrations of chromatid type (nature), in cells that come in
mitosis from phase G 1 (pre-synthesis) occur aberrations of chromosome type (double
bridges, paired fragments at anaphase).
Under treatment by chemical mutagens of asynchronous cell cultures, no rear-
rangements detect during the ¿ rst 2-4 hr (depending on the duration of G 2 phase at
different objects). This phenomenon is named “delayed” effect. The chromosomal re-
arrangements appear later after the entry to mitosis of cells treated at the beginning
or during DNA synthesis (phase S) or before phase S (named pre-synthetic phase G 1 ).
Chromosome rearrangements are usually analyzed in the ana-telophases or meta-phas-
es. A large number of chromosomes in many objects complicate the identi¿ cation of
chromosome aberrations in metaphase plates. In this case fragments of chromosomes
or broken bridges cannot be identi¿ ed. In this case, scientists analyze the anaphase and
telophases (ana-telophase method).
For the estimate of environmental contamination the method of analyzes of ana-
telophases is suf¿ cient. An example is the estimation of pollution in the industrial area
of the city of Staryj Oskol on the meristem of birch [8].
In Moscow 1960-1970s, extensive cytogenetic studies of chemical and radiation
mutagenesis were carried N. P. Dubinin, his colleagues and followers. The work was
begun in the laboratory of radiation genetics of Institute of biophysics of Academy of
Science the USSR and continued in Institute of general genetics. A large number of
articles and monographs about cytogenetic effects of ionizing radiation or chemical
compounds were published [9]). N. P. Dubinin formulated the idea of the mechanism
of action of chemical mutagens, mutagens cause potential changes in the chromosomes