Bacteria : Clones and Mutation 



339 



QUESTIONS FOR DISCUSSION 



36.1. Which single characteristic of bacteria provides the greatest advantage for genetic 

 studies? Why? 



36.2. Has any evidence been presented, in previous Chapters, that spontaneous mutations 

 are preadaptive? If so, state where. 



36.3. Suppose 1000 streptomycin-free test tubes are each inoculated with one bacterium 

 of a streptomycin-sensitive clone. Growth is permitted until there are about one 

 billion bacteria present in each tube. The contents of each tube are then plated on 

 streptomycin-containing agar. 



What kind of result would you expect if mutations to streptomycin-resistance were 

 postadaptive in origin? Preadaptive in origin? Could you distinguish between these 

 two alternatives from the results expected? How? 



36.4. Is it valid to conclude, from our discussion of drug-resistant mutants, that no drugs 

 are mutagenic? Explain. 



36.5 On the assumption that all members of a clone are identical, genetically and physi- 

 ologically, has there been any opportunity for sexual processes to influence the results 

 of any of the experiments described in the present Chapter? Explain. 



36.6. Discuss the causes of the "spontaneous" mutation rate. 



36.7. Does this Chapter offer any new evidence that the genotype regulates its own muta- 

 bility? Explain. 



36.8. What, if any, new information does the present Chapter provide you with regard to 

 the genetic or chemical basis of mutation? 



Joshua Lederberg and Esther Marilyn Lederberg about 1951. {Courtesy of 

 The Long Island Biological Association.) 



