The Genetic Effects Of Radiation - free ebook by Isaac Asimov

The Genetic Effects of Radiation

By ISAAC ASIMOV and THEODOSIUS DOBZHANSKY...

3 minute read

Read Chapter

THE COVER

The cover design embodies a radiation symbol, a stylized karyotype of human chromosomes, and a genealogical table....

6 minute read

Read Chapter

THE AUTHORS

ISAAC ASIMOV received his academic degrees from Columbia University and is Associate Professor of Biochemistry at the Boston University School of Medicine. He is a prolific author who has written over 65 books in the past 15 years, including about 20 science fiction works, and books for children. His many excellent science books for the public cover subjects in mathematics, physics, astronomy, chemistry, and biology, such as The Genetic Code , Inside the Atom , Building Blocks of the Universe ,

1 minute read

Read Chapter

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, e

2 minute read

Read Chapter

Cells and Chromosomes

The average human adult consists of about 50 trillion cells —50 trillion microscopic, more or less self-contained, blobs of life. He begins life, however, as a single cell, the fertilized ovum . After the fertilized ovum is formed, it divides and becomes two cells. Each daughter cell divides to produce a total of four cells, and each of those divides and so on. There is a high degree of order and direction to those divisions. When a human fertilized ovum completes its divisions an adult human be

2 minute read

Read Chapter

Enzymes and Genes

Each cell is a tiny chemical factory in which several thousand different kinds of chemical changes are constantly taking place among the numerous sorts of molecules that move about in its fluid or that are pinned to its solid structures. These chemical changes are guided and controlled by the existence of as many thousands of different enzymes within the cell. Enzymes possess large molecules built up of some 20 different, but chemically related, units called amino acids . A particular enzyme mol

3 minute read

Read Chapter

Parents and Offspring

How does the fertilized ovum obtain its particular set of chromosomes in the first place? Each adult possesses gonads in which sex cells are formed. In the male, sperm cells are formed in the testes; in the female, egg cells are formed in the ovaries. In the formation of the sperm cells and egg cells there is a key step— meiosis —a cell division in which the chromosomes group into pairs and are then apportioned between the daughter cells, one of each pair to each cell. Such a division, unaccompa

1 minute read

Read Chapter

Sudden Change

Shifts in chromosome combinations, with or without crossovers, can produce unique organisms with characteristics not quite like any organism that appeared in the past nor likely to appear in the reasonable future. They may even produce novelties in individual characteristics since genes can affect one another, and a gene surrounded by unusual neighbors can produce unexpected effects. Matters can go further still, however, in the direction of novelty. It is possible for chromosomes to undergo mor

4 minute read

Read Chapter

Spontaneous Mutations

Mutations that take place in the ordinary course of nature, without man’s interference, are spontaneous mutations . Most of these arise out of the very nature of the complicated mechanism of gene replication. Copies of genes are formed out of a large number of small units that must be lined up in just the right pattern to form one particular gene and no other. Ideally, matters are so arranged within the cell that the necessary changes giving rise to the desired pattern are just those that have a

4 minute read

Read Chapter

Genetic Load

Some gene mutations produce characteristics so undesirable that it is difficult to imagine any reasonable change in environmental conditions that would make them beneficial. There are mutations that lead to the nondevelopment of hands and feet, to the production of blood that will not clot, to serious malformations of essential organs, and so on. Such mutations are unqualifiedly bad. The badness may be so severe that a fertilized ovum may be incapable of development; or, if it develops, the fetu

4 minute read

Read Chapter

Mutation Rates

It is easier to observe the removal of genes through death or through failure to reproduce than to observe their production through mutation. It is particularly difficult to study their production in human beings, since men have comparatively long lifetimes and few children, and since their mating habits cannot well be controlled. For this reason, geneticists have experimented with species much simpler than man—smaller organisms that are short-lived, produce many offspring, and that can be penne

3 minute read

Read Chapter

Ionizing Radiation

Our modern technological civilization exposes mankind to two general types of genetic dangers unknown earlier: Synthetic chemicals (or unprecedentedly high concentrations of natural ones) absent in earlier eras, and intensities of energetic radiation equally unknown or unprecedented. Chemicals can interfere with the process of replication by offering alternate pathways with which the cellular machinery is not prepared to cope. In general, however, it is only those cells in direct contact with th

5 minute read

Read Chapter

Background Radiation

Ionizing radiation in low intensities is part of our natural environment. Such natural radiation is referred to as background radiation . Part of it arises from certain constituents of the soil. Atoms of the heavy metals, uranium and thorium, are constantly, though very slowly, breaking down and in the process giving off alpha rays, beta rays, and gamma rays. These elements, while not among the most common, are very widely spread; minerals containing small quantities of uranium and thorium are t

3 minute read

Read Chapter

Man-made Radiation

Man began to add to the background radiation in the 1890s. In 1895, X rays were discovered and since then have become increasingly useful in medical diagnosis and therapy and in industry. In 1896, radioactivity was discovered and radioactive substances were concentrated in laboratories in order that they might be studied. In 1934, it was found that radioactive forms of nonradioactive elements ( radioisotopes ) could be formed and their use came to be widespread in universities, hospitals, and in

2 minute read

Read Chapter

Radiation Sickness

The danger to the individual as a result of overexposure to high-energy radiation was understood fairly soon but not before some tragic experiences were recorded. One of the early workers with radioactive materials, Pierre Curie, deliberately exposed a patch of his skin to the action of radioactive radiations and obtained a serious and slow-healing burn. His wife, Marie Curie, and their daughter, Irène Joliot-Curie, who spent their lives working with radioactive materials, both died of leukemia,

2 minute read

Read Chapter

Radiation and Mutation

Where radiation is insufficient to render a cell incapable of division, it may still induce mutations, and it is in this fashion that skin cancer, leukemia, and other disorders may be brought about. [6] Studies at the California Institute of Technology furnish information on the nature of radiation effects on genes. The experiments produced fruit flies with three or four wings and double or partially doubled thoraxes by causing gene mutation through X-irradiation and chromosome rearrangements. A

4 minute read

Read Chapter

Dosage Rates

Another difference between the genetic and somatic effects of radiation rests in the response to changes in the rate at which radiation is absorbed. It makes a considerable difference to the body whether a large dose of radiation is absorbed over the space of a few minutes or a few years. When a large dose is absorbed over a short interval of time, so many of the growing tissues lose the capacity for cell division that death may follow. If the same dose is delivered over years, only a small bit

3 minute read

Read Chapter

Effects on Mammals

Although genetic findings on such comparatively simple creatures as fruit flies and bacteria seem to apply generally to all forms of life, it seems unsafe to rely on these findings completely in anything as important as possible genetic damage to man through radiation. During the 1950s and 1960s, therefore, there have been important studies on mice, particularly by W. L. Russell at Oak Ridge National Laboratory, Oak Ridge, Tennessee. While not as short-lived or as fecund as fruit flies, mice can

4 minute read

Read Chapter

Conclusion

It is unrealistic to suppose that all sources of man-made radiation should be abolished. The good they do now, the greater good they will do in the future, cannot be abandoned. It is, however, reasonable to expect that the present Nuclear Test Ban Treaty will continue and that nations, such as France and China, which have nuclear capabilities but are not signatories of the Treaty will eventually sign. It is also reasonable to expect that X ray diagnosis and therapy will be carried on with the gr

4 minute read

Read Chapter

Books

Radiation, Genes, and Man , Bruce Wallace and Theodosius Dobzhansky, Holt, Rinehart and Winston, Inc., New York 10017, 1963, 205 pp., $5.00 (hardback); $1.28 (paperback). Genetics in the Atomic Age (second edition), Charlotte Auerbach, Oxford University Press, Inc., Fair Lawn, New Jersey 07410, 1965, 111 pp., $2.50. Atomic Radiation and Life (revised edition), Peter Alexander, Penguin Books, Inc., Baltimore, Maryland 21211, 1966, 288 pp., $1.65. The Genetic Code , Isaac Asimov, Grossman Publishe

1 minute read

Read Chapter

Articles

Genetic Hazards of Nuclear Radiations, Bentley Glass, Science , 126: 241 (August 9, 1957). Genetic Loads in Natural Populations, Theodosius Dobzhansky, Science , 126: 191 (August 2, 1957). Radiation Dose Rate and Mutation Frequency, W. L. Russell and others, Science , 128: 1546 (December 19, 1958). Ionizing Radiation and the Living Cell, Alexander Hollaender and George E. Stapleton, Scientific American , 201: 95 (September 1959). Radiation and Human Mutation, H. J. Muller, Scientific American ,

27 minute read

Read Chapter

Motion Pictures

Radiation and the Population , 29 minutes, sound, black and white, 1962. Produced by the Argonne National Laboratory. This film explains how radiation causes mutations and how these mutations are passed on to succeeding generations. Mutation research is illustrated with results of experimentation on generations of mice. A discussion of work with fruit flies and induced mutations is also included. This film is available for loan without charge from the AEC Headquarters Film Library, Division of P

3 minute read

Read Chapter

UNITED STATES ATOMIC ENERGY COMMISSION

Nuclear energy is playing a vital role in the life of every man, woman, and child in the United States today. In the years ahead it will affect increasingly all the peoples of the earth. It is essential that all Americans gain an understanding of this vital force if they are to discharge thoughtfully their responsibilities as citizens and if they are to realize fully the myriad benefits that nuclear energy offers them. The United States Atomic Energy Commission provides this booklet to help you

1 minute read

Read Chapter