Genetic Effects of Radiation

(radiation mutagenesis), the emergence of hereditary changes when organisms are irradiated. The genetic effect of radiation is an important part of the biological effect of ionizing radiation studied by radiation genetics. The first stable “radioraces” in yeasts were obtained by the Soviet biologists G. A. Nadson and G. S. Filippov in 1925. Data on increased frequency of mutation in fruit flies (Drosophila) under X-radiation were published by the American geneticist H. Muller in 1927.

The mutagenic effect is produced by all types of ionizing radiation, as well as by ultraviolet rays, if the hereditary structures of any organisms—from viruses and bacteria to highly organized animals, including man—are subjected to them. Moreover, in complex organisms mutations may arise both in the sex cells, the gametes, and in the body cells, or somatic cells. Radiation may produce all types of mutations (gene, chromosomal, genomic, and cytoplasmic). Within a particular range of dosages the frequency of mutation increases proportionally to the radiation dosage. When the dosage is increased beyond a certain value the linearity of the curves describing mutation frequency as a function of dosage is destroyed. The newly induced mutations are usually recessive and harmful. An increase in the radioactive background leads to the accumulation of latent harmful mutations in populations of organisms, including those of man.

An important practical application of the genetic effects of radiation is radiation selection, that is, the selection of economically valuable mutations obtained from cultivated plants and industrial microorganisms that have been exposed to radiation. New varieties of oats, barley, peas, peanuts, fruits, and ornamental plants developed by this method are already being cultivated on a large scale. Many highly productive industrial strains of microorganisms—producers of antibiotics, vitamins, and amino acids—have also been obtained by means of radiation mutagenesis.