XIV CONTENTS 



c. Mutations affecting requirements for ad- 

 sorption 301 



d. Mutations affecting lysis-inhibition 302 



e. Mutations affecting plaque type 304 



f. Mutations affecting stability 305 



g. Mutations affecting antigenic specificity. . . , 305 

 h. Other mutations 306 



4. Mutation frequency 308 



5. Mutagenic agents 310 



6. Summary 317 



XVII Mixed Infection 319 



1. Mixed infection with unrelated phages — mutual 

 exclusion 320 



2. Mixed infection with related phages 325 



a. Absence of mutual exclusion 325 



b. Partial exclusion 327 



c. Limited participation 329 



3. Summary 329 



XVIII Bacteriophage Genetics 331 



1. Mixed infection and recombination 331 



2. The vegetative phage pool 333 



3. The Visconti-Delbriick theory 335 



a. Many genetic loci are available 335 



b. Complementary recombinants are formed . . 335 



c. Multiple recombinations 336 



d. Linkage and negative interference 337 



e. Multiplication after recombination 338 



f. Drift toward genetic equilibrium 340 



g. A problem in population genetics 342 



4. Heterozygosis 344 



5. Pseudoallelism 351 



a. The gene as a functional unit 352 



b. The mutational unit 354 



c. The unit of recombination 356 



6. Radiation genetics 357 



a. Multiplicity reactivation of phage inacti- 

 vated by ultraviolet light 357 



b. Multiplicity reactivation of phage inacti- 

 vated by ionizing radiations or by P^" decay 362 



