The Episome F 329 



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QUESTIONS FOR DISCUSSION 



24.1. What events do you suppose occur from the time donor DNA enters a female 

 conjugant to the appearance of a segregant haploid for a segment of the donor 

 DNA? 



24.2. What is the evidence that F can integrate in a chromosome? That it can do 

 the reverse (deintegrate)? 



24.3. What properties are attributable to F when integrated at a chromosomal locus? 



24.4. Does the occurrence of spontaneous ruptures of the donor bacterial chromo- 

 some interfere with mapping the linear order of genes via artificial interruptions 

 of mating? Explain. 



24.5. Assume (correctly) that the decay of P 32 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. 



24.6. What kinds of evidence can you present that a nuclear body of E. coli normally 

 contains a single chromosome? A ring chromosome? 



24.7. Give the genotypes of parents and recombinants and the specific culture condi- 

 tions you would employ in searching the progeny of F+ by F^ crosses for Hfr 

 lines. 



24.8. What relationships exist between episomes and genetic recombination? 



24.9. Transforming DNA is isolated from cultures of Bacillus subtilis in a stationary 

 (nonreplicating) phase and in an exponentially-growing and nonsynchronously- 

 reproducing phase and tested with respect to eleven genetic markers. Invent 

 quantitative results expected if the chromosome replicates in a polarized manner. 



