Long before Puck and Marcus (1955,1956; Puck et al., 1956,1957) published their series of papers on the techniques for culturing single mammalian cells, which opened the way to the study of the action of ionizing radiation on the survival of eukaryotic cells, the radiobiology of eukaryotic cells had been dominated by two specific fields. One was concerned with the study of inheritable mutations in insects, notably Drosophila (Muller, 1930, 1940; Muller and Herskowitz, 1954). The other was concerned with the measurement of chromosomal aberrations, especially in plant cells (Sax, 1939, 1940, 1941; Lea, 1946; Lea and Catcheside, 1942; Catcheside, 1938; Catcheside and Lea, 1943; Catcheside et al., 1946; Thoday, 1942; Stadler, 1928, 1930; Swanson, 1940,1942,1943; McClintock, 1941 a, b). The occurrence of chromosome structural changes in plant cells, which could be observed in cells which were fixed and stained at the first mitosis after irradiation, provided an early, direct, visible and quantitative measurement of the effect of radiation on the cell. These observations and quantitative measurements led to the first theoretical formulations on the mechanisms involved in the formation of the radiation-induced chromosome structural changes which gave rise to the “Classical” theory of chromosomal aberrations. Later observations, also made on chromosomal aberrations induced in plant cells, led to the formulation of the “Exchange” theory (Revell, 1955, 1959, 1963, 1966, 1974) which gives a different interpretation of the formation of radiation-induced chromosome structural changes. Both of these theories were developed prior to the recent investigations on the molecular structure of the chromosome, but Bender and his colleagues (Bender et al., 1973 a, b, 1974) have updated the classical theory in terms of the unineme concept of chromosome structure and have at the same time expanded the theory to explain aberrations which are induced by chemicals and ultra-violet radiation.
KeywordsRecombination Caffeine Cesium Saccharomyces Colchicine
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