: The Genetic Effects of Radiation by Asimov Isaac Dobzhansky Theodosius - Radiogenetics

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The Genetic Effects of Radiation

Contents

THE MACHINERY OF INHERITANCE 1 Introduction 1 Cells and Chromosomes 2 Enzymes and Genes 5 Parents and Offspring 8 MUTATIONS 10 Sudden Change 10 Spontaneous Mutations 13 Genetic Load 16 Mutation Rates 19 RADIATION 22 Ionizing Radiation 22 Background Radiation 27 Man-made Radiation 30 DOSE AND CONSEQUENCE 32 Radiation Sickness 32 Radiation and Mutation 33 Dosage Rates 37 Effects on Mammals 40 Conclusion 43 SUGGESTED REFERENCES 47

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The Genetic Effects of Radiation

THE MACHINERY OF INHERITANCE

Introduction

There is nothing new under the sun, says the Bible. Nor is the sun itself new, we might add. As long as life has existed on earth, it has been exposed to radiation from the sun, so that life and radiation are old acquaintances and have learned to live together.

We are accustomed to looking upon sunlight as something good, useful, and desirable, and certainly we could not live long without it. The energy of sunlight warms the earth, produces the winds that tend to equalize earth's temperatures, evaporates the oceans and produces rain and fresh water. Most important of all, it supplies what is needed for green plants to convert carbon dioxide and water into food and oxygen, making it possible for all animal life to live.

Yet sunlight has its dangers, too. Lizards avoid the direct rays of the noonday sun on the desert, and we ourselves take precautions against sunburn and sunstroke.

The same division into good and bad is to be found in connection with other forms of radiation--forms of which mankind has only recently become aware. Such radiations, produced by radioactivity in the soil and reaching us from outer space, have also been with us from the beginning of time. They are more energetic than sunlight, however, and can do more damage, and because our senses do not detect them, we have not learned to take precautions against them.

To be sure, energetic radiation is present in nature in only very small amounts and is not, therefore, much of a danger. Man, however, has the capacity of imitating nature. Long ago in dim prehistory, for instance, he learned to manufacture a kind of sunlight by setting wood and other fuels on fire. This involved a new kind of good and bad. A whole new technology became possible, on the one hand, and, on the other, the chance of death by burning was also possible. The good in this case far outweighs the evil.

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