Chapter Vm 

 Bacteriophage Genetics 



Cyrus Levinthal 



Biology Department, Massachusetts Institute of Technology, Cambridge, 



Massachusetts 



I. Introduction 281 



II. Phage Mutations 282 



A. Plaque-Type Characters 282 



B. Host-Range Mutants 284 



III. Recombination 285 



A. Linkage Map 285 



B. Techniques of Phage Crosses 286 



C. Two-Factor Crosses 287 



D. Three-Factor Cross 289 



IV. Multiple Matings in Individual Crosses 290 



V. The Mating Event 293 



A. Reciprocal Recombinants 294 



B. Heterozygotes 296 



C. Radioactive Tracer Experiments 299 



VI. Mating Kinetics 302 



A. General Assumptions 302 



B. Distribution of Mutants 303 



C. Distribution of Recombinants 304 



D. The Mating Process 304 



E. Distribution of Recombinants for Close Markers 306 



VII. Fine Structure Genetics 307 



A. The rll System 307 



B. Deletions 308 



C. Function Units 309 



D. Negative Interference 310 



VIII. Phenotypic Variations 311 



A. Phenotypic Mixing 311 



B. Host-Controlled Variation 312 



IX. Conclusion 313 



References 316 



I. Introduction 



Phage genetics is at present the subject of a rather profound disagreement 

 among the workers in the field. The disagreement is not about experimental 

 results and is only partly connected with the direct interpretation and calcu- 

 lation of the results. It is more a disagreement about the prospects for the 

 immediate future. There are some who feel that most of the essential results 



281 



