354 CHAPTER 26 



26.7. In what respects is d>\ similar to and different from an I particle? 



26.8. A temperate phage able to transduce any known chromosomal marker in E. coli 

 is known. Would you be able to locate the chromosomal site for its prophage? 

 I \plain. 



26.9. Does the finding — that a single phage particle can transduce a bacterial fragment 

 carrying not onlj a bacterial marker hut two linked prophages — have any bear- 

 ing upon the essentiality of the entire phage genome being present for infection 

 and or the production o\ phage progeny? Explain. 



26.10. How can you distinguish a <£T4 mutant in the ill region from one in the rl or 

 the rill region'.' 



26.1 I. Describe how the cis-trans test is used to show functional complementation be- 

 tween two mutants in phage. 



26.12. What would you expect to be the near-maximum number of nucleotides trans- 

 duceable by a phage still capable of phage activity? On what is your opinion 

 based? 



26.13. If the average protein-specifying gene were 2000 nucleotides long, how many 

 different proteins could be specified by ^>T4? By <£X174? 



2(^.14. What do you consider to be the most remarkable feature of </>X174? 



26.15. Mutants which show functional complementation in the pan-2 region of Neu- 

 rospora can be arranged in the same linear order by complementation and by 

 genetic recombination. Is it necessarily true that both maps will also be iden- 

 tical for other regions? Explain. 



26.16. What is a functional genetic unit, or cistron? How is your answer related to 

 its length in nucleotides? 



26.17. What have you learned in this chapter regarding the chemical scope of the 

 genetic unit of recombination? Of function? 



