( HAPTER 27 



QUESTIONS FOR DISCUSSION 



2". I. Do .ill matings transfer F particles oi one genotype or another? Explain. 



27.2. Discuss the relationship between the transmission ol tree F particles and a seg- 

 ment of the male chromosome. 



27.3. Discuss the realit) of a bacterial "chromosome" and its linear arrangement. 



27.4. B\ what series of events can you explain the origin of strain P4.\-l from P4x? 



27.5. From which particular Htr strain of E. coli could you obtain an F-Pro (pro- 

 line) merogenote? How'.' 



27.6. How do \ou suppose episomes originate? 



27.7. Are integrated episomes and episomal derivatives generally able to break chro- 

 mosomes? Explain. 



27.8. It has been found that c/>P2. a temperate phage which normally integrates at 

 a particular chromosomal locus, position I, loses the extreme preference for 

 position I when liberated from a strain carrying it in position II. How can you 

 explain this finding? 



27.9. Discuss the statement: "The ability to pass from the integrated to the free state 

 or vice versa is possessed by every gene in a bacterial cell." 



27. 1U. A transducing phage can carr\ two closely-linked prophages obtained from a 

 doubly-lysogenic host. What conclusions can you draw with regard to the nu- 

 cleotide content of a mature phage and a prophage? 



27.11. The Lac gene can either be chromosomal when integrated into the chromosome, 

 or extrachromosomal when attached to free F. Should such a gene be consid- 

 ered an episome? Why? 



27.12. How would you locate the position of the UV-inducible prophage of <£434 in the 

 E. coli linkage map? 



27.13. How would you locate the prophage site of a noninducible (by ultraviolet light 

 or zygote formation ) phage? 



27.14. Lactic dehydrogenase contains a single-strand sequence of about 33 deoxyribo- 

 tides. Should this portion of the enzyme be considered genetic material? Ex- 

 plain. 



27.15. During conjugation. F is reported to enhance the transfer to the F~ cell such 

 substances as lactose, ultraviolet-irradiation products that induce A prophage, 

 and a A repressor. Is F acting as a promoter in these cases? Explain. 



