METHODS TO ESTIMATE THE GENETIC RISK
In this chapter those effects are considered that may be inherited through radiation or chemically induced injury to the genes or chromosomes of germ cells. Mutational changes represent a broad spectrum of alterations in the deoxyribonucleotide structure of the genes. At one end of the spectrum thischange can be represented by a single nucleotide base substitution, base addition or deletion. At the other end of the mutation spectrum is a complete deletion of the entire gene and/or adjacent genes. For higher organisms these submicroscopic changes are not further resolvable in many instances, and they are simply classified as mutations. All organisms are the products of a long evolutionary history during which favorable genes have been preserved and deleterious genes eliminated by natural selection. Beneficial mutations of the past are part of the present population. A random change is much more likely to be deleterious than to improve the fitness. In the framework of genetic possibility, a mutation is essentially a random change. Therefore, the general harmfulness of mutation is both an empirical fact and an expectation based on evolutionary reasoning. The Mendelian mechanism is remarkably effective in maintaining variability. Crow (1981) emphasized that if any way of reducing the spontaneous mutation rate can be found, it could have enormous humanitarian benefits. Based on this reasoning we have to avoid an increase of the spontaneous human mutation rate due to the exposure to ionizing radiations and chemical mutagens. To prevent an increase in the mutation rate, for chemical mutagens, the first step is the Hazard Identification, the determination of whether a substance is mutagenic. The second step is the Hazard Evaluation, the investigation of the chemical, physical, and biological factors that affect mutagenesis. The third step is the "Risk Estimation", the estimation of effect per unit of exposure. The risk estimation can be divided into two components: estimation of mutagenic effects on germ cells (damage) and estimation of effects on health and welfare of future generations (impact). The Hazard Evaluation and the Risk Estimation are also relevant for the exposure to ionizing radiation. Both aspects will be discussed in detail in this chapter.
Bibliographic Reference: MUTATIONS IN MAN, 1984, PP. 293-318 PUBLISHED BY SPRINGER-VERLAG, HEIDELBERG (GERMANY)
Record Number: 1989122080600 / Last updated on: 1987-01-01
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