250 CHAPTER 28 



Natural and manmade penetrating radiations are doubtless causing mutations in our 

 somatic and germ cells, increasing our load of detrimental mutants. This exposure, though 

 detrimental, is most likely no threat to man's survival as a species at present, although it 

 could be in the future, if it became large enough. Further research is needed to assess 

 accurately the magnitude of the effect of manmade radiations and chemical substances upon 

 his mutation rate and well-being. 



REFERENCES 



Auerbach, C, Genetics in the Atomic Age, Fair Lawn, N.J., Essential Books, 1956. 



Background Material for the Development of Radiation Protection Standards, Report No. 1, 

 Federal Radiation Council, U.S. Government Printing Office, Washington, D.C., 

 1960. 



Chu, E. H. Y., Giles, N. H., and Passano, K., "Types and Frequencies of Human Chromo- 

 some Aberrations Induced by X-rays," Proc. Nat. Acad. Sci., U.S., 47:830-839, 1961. 



Crow, J. F., "Ionizing Radiation and Evolution," Scient. Amer., 201:138-160, 1959. 



Dobzhansky, Th., Evolution, Genetics, and Man, New York, John Wiley & Sons, 1955. 



Herskowitz, I. H., "Birth Defects and Chromosome Changes," Nuclear Information, 3 



(No. 2):l-2, 4, 1960. 

 Krieger, H., and Freire-Maia, N., "Estimate of the Load of Mutations in Homogeneous 



Populations from Data on Mixed Samples," Genetics, 46:1565-1566, 1961. 

 Morton, N. E., "The Mutational Load Due to Detrimental Genes in Man," Amer. J. 



Human Genet., 12:348-364, 1960. 

 MuUer, H. J., "Mutational Prophylaxis," Bull. N.Y. Acad. Med., 2nd Ser., 24:447-469, 



1948. 

 MuUer, H. J., "Radiation Damage to the Genetic Material," Amer. Scientist, 38:33-59, 126, 



399-425, 1950. 

 Report of the United Nations Scientific Committee on the Effects of Atomic Radiation, New 



York: General Assembly Official Records: 13th Session, Suppl. 17 (A/3838), 



Chaps. 5-6, Annexes G-I, 1958. 

 Selected Materials on Radiation Protection Criteria and Standards: Their Basis and Use, 



Joint Committee on Atomic Energy, Congress of the United States, U.S. Govern- 

 ment Printing Office, Washington, D.C., 1960. 



The Biological Effects of Atomic Radiation. Simvnary Reports, National Academy of 

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 Reports of the Genetics Committee.) 



QUESTIONS FOR DISCUSSION 



28.1. Do you suppose that the mutations which occur in man serve a useful function? 

 Why? 



28.2. Compare the fate of a mutational load in asexually reproducing populations that 

 are haploid, diploid, and autotetraploid. 



28.3. Discuss the effect upon the gene pool of mutants restricted to the somatic line. 



28.4. Can the gene that comprises part of a detrimental equivalent also comprise part of a 

 lethal equivalent? Explain. 



28.5. Give examples of polymorphism, and of balanced polymorphism in the genetics 

 of man. 



