")(»(» CHAPTER 40 



QUESTIONS FOR DISCUSSION 



40.1. What is t ho function ol a nucleus (such as in the cluck erythrocyte) whose DNA 

 seems to be almost completely complexed with histone? 



40.2. Discuss the correlation between the inciting temperatures of DNA complexed 

 with basic proteins and the inhibition ol gene activity. 



40.3. What interpretation can you give to the observation of H. Busch that many 

 kinds ol tumors show a high synthesis rate of lysine-rich histone? 



40.4. How do you explain the observation of P. R. Gross that in unfertilized sea urchin 

 eggs, concentrations o\ actinomycin D (which apparently completely inhibit mes- 

 senger RNA production) reduce but do not completely inhibit protein synthesis.' 



40.5. Discuss the genetic and environmental factors which influence the pulling pattern 

 in the polynemic chromosomes of larval Diptera. 



40.6. Discuss the role of "feedback" in the molecular control of genetic activity. 



40.7. What can you conclude about gene action from the observation that the histones 

 associated with clumped chromatin show a smaller amount of acetylation per 

 milligram than histones isolated from diffuse chromatin? 



40.8. Can you explain why a particular DNase digests clumped but not diffuse 

 chromatin? 



40.9. How can you explain that in animal sperm the chromosomes are inactive even 

 when they contain deoxyribonucleoprotamines in place of deoxyribonucleo- 

 histones? 



40.10. R. S. Chang, P. Goldhaber, and T. H. Dunnebacher (Proc. Nat. Acad. Sci., 

 U.S., 52:709-715, 1964) were able to propagate continuously (for at least two 

 years) cultures of human liver cells that were uninfected or infected with lipo- 

 virus. They found, however, that the infected cells contained no more than 

 10 per cent of the DNA of uninfected parent cells. What, if anything, do these 

 results suggest about: 



(a) genetic content necessary for maintenance of cell integrity and replication? 



(b) chromosomal polynemy? 



40.11. Under what conditions might cells use single-stranded DNA as a template for 

 protein synthesis? 



