Author: National Research Radiation
Publisher: Theclassics.Us
Published: 2013-09
Total Pages: 74
ISBN-13: 9781230227474
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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1981-12-01 edition. Excerpt: ...type of change is found in the induced release of virus particles from cells irradiated with ionizing radiation (Shinagawa et al., 1977) and in the induction of enzyme systems (see Hanawalt et al., 1979, for UV induction of repair enzymes in bacteria and mammalian cells). In both of these examples, many or all of the exposed cells experience a similar change in response to radiation. A second class of change includes those alterations that differ from one cell to another. A wide variety of possible discrete changes, such as mutations, is possible. Any single cell may or may not have experienced one or another of the changes, and the probability of finding a cell with a specific change would be expected to be dose-dependent. Such changes resulting from exposures to UV-irradiation and chemicals include mutations that are the result of DNA damage or flawed repair of the lesions. The heritability of such changes permit their identification as mutants. Some such changes may be sufficiently drastic to compromise the viability of the cell. Lethal effects of radiation exposure may include a large array of these drastic changes, each different and each lethal. Under these conditions, efforts at extrapolation require knowledge of the number and types of changes and their consequences for biological reactions such as DNA replication and RNA transcription. Much more insight into these issues is necessary because changes in DNA and in other cellular structures are not necessarily stable, but may change with time. Consideration must be given to the rates of spontaneous decay of lesions, rates of repair, and rates of cell replication and of DNA transcription. In mammalian systems, repair of excisions and strand breaks occurs in nondividing cells....