Bacteria: Recombination {III) 365 



39.4. Does the occurrence of spontaneous ruptures of the donor bacterial chromosome 

 interfere with mapping the linear order of genes via artificial interruptions of mating? 

 Explain. 



39.5. Assume, correctly, that the decay of P^' incorporated into DNA can break the E. coli 

 chromosome, and that this decay is temperature-independent. Devise an experiment 

 to determine the gene order in this bacterium. 



39.6. What kinds of evidence can you present that per nucleus of £^. coli there is normally: 



a. A single "chromosome"? 



b. That this is a ring? 



39.7. Give the genotypes of parents and recombinants, and the specific culture conditions 

 you would employ in searching the progeny of F+ X F~ crosses for Hfr lines. 



39.8. Would you, in the light of our knowledge of episomes, revise the discussion on p. 198 

 regarding recon polarity? Why? 



39.9. What relationships exist between episomes and genetic recombination? 



