45(J CHAPTER 35 



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QUESTIONS FOR DISCUSSION 



35.1. Why should Kornberg and his associates fail to observe extended DNA synthesis 

 in extracts of T2-infected cells to which the deoxyriboside 5'-triphosphates of A, 

 T, G, and C had been added? How would you proceed to obtain the desired 

 synthesis? 



35.2. What have we learned about the genetic control of nucleic acid synthesis from 

 in vitro studies? 



35.3. Do you suppose there is a genetic control over the tautomeric states a base in 

 DNA may exhibit? Justify your opinion. 



35.4. Whereas laboratory synthesis of nucleosides can produce a mixture of « and ft 

 configurations (which differ in the way the parts are folded or pointed relative 

 to each other), all the nucleosides in DNA have the ft configuration. How can 

 you explain this difference? 



35.5. Outline experiments designed to throw light upon the genetics of 



( a ) DNA polymerase 



( b ) RNA synthetase 



(c) RNA polymerase 



(d) polynucleotide phosphorylase 



35.6. Which do you think came first in evolution, biochemical pathways leading to 

 DNA or to RNA synthesis? Explain. 



35.7. Many mutants induced by nitrous acid in TMV show a mutant phenotype but 

 no change in the amino acid sequence of their protein coat. Suggest ways in 

 which such mutants produce their phenotypic effects. 



35.8. Does the work with metagons suggest an origin for viruses? Explain. 



