184 CHAPTER 21 



REFERENCES 



Bacq, Z. M., and Alexander, P., Fundamentals of Radiobiology, 2nd Ed., New York, Per- 

 gamon Press, 1961. 



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. 



"Ionizing Radiation," Scient. Amer., 201 :No. 3 (Sept.), 1959. 



MuUer, H. J., "General Survey of Mutational Effects of Radiation," in Radiation Biology 

 and Medicine, Claus, W. D. (Ed.), Reading, Mass., Addison-Wesley, Chap. 6, 

 pp. 145-177. 



Puck, T. T., "Radiation and the Human Cell," Scient. Amer., 202, No. 4:142-153, 1960. 



Sparrow, A. H., Binnington, J. P., and Pond, V., Bibliography on the Effects of Ionizing Radia- 

 tions on Plants, 1896-1955, Brookhaven Nat. Lab. Publ. 504 (L-103), 1958. 



QUESTIONS FOR DISCUSSION 



21.1. Why should tissue, which is only about ten times as dense as air, have about one 

 thousand times the number of ionizations in it as has air, when both are given the 

 same radiation exposure? 



21.2. What evidence can you give to support the view that the ions causing breakage need 

 not always attack the chromosome directly? 



21.3. Does the observation that the volume of a chromosome is variable under different 

 conditions mean that it has an inconstant gene content? Explain. 



21.4. Do you suppose that chromosomes exposed to X rays are more likely to undergo 

 structural change when they are densely spiralized than when they are relatively 

 uncoiled? Why? 



21.5. Discuss the role of heterochromatin in changes involving chromosome number and 

 chromosome shape. 



21.6. Do you suppose the oxygen content of a space capsule could affect the mutability of 

 Drosophila passengers? Explain. 



21.7. Discuss the relative efficiency, per r, of small doses of X rays and of fast neutrons 

 in producing structural changes in chromosomes. 



21.8. Do you suppose that the mutability of ultraviolet light threatens man's survival? 

 Explain. 



21.9. Compare the breakages and their consequences caused by the same dose of X rays 

 administered to: 



a. A polyploid and a diploid liver cell in man. 



b. A diploid neuron in man and Drosophila. 



c. A sperm and a spermatogonium in man. 



21.10. How could you locate the position of the gene for white eye in the salivary X chromo- 

 some of Drosophila using: 



a. DitTerent small deletions? 



b. Overlapping inversions? 



