Chapter XI 



Genetic Interactions between Animal Viruses 



F. M. Burnet 

 Walter and Eliza Hall Institute, Melbourne 



I. Introduction 275 



II. The Different Types of Genetic Interaction 276 



III. The Technical Requirements in Virus Genetics 277 



A. Pure Clone Isolations 277 



B. Marker Characteristics 279 



1. Morphological 279 



2. Somatic 279 



3. Reproductive 280 



4. Incidental 280 



C. Principles of Recombination Experiments 280 



IV. Genetic Interactions within the Myxovirus Group 282 



A. Historical 282 



B. Available Markers in the Influenza Viruses 283 



C. Interchange of Linkage Groups 285 



D. Pkenotypic Mixture and Heterozygosis 286 



E. Use of Nonviable Virus as an Effective "Parent" 288 



P. Redistribution of Virulence 289 



1 . Transfer of Neuropathogenicity 290 



2. Redistribution of Mouse Lung Virulence (MLV) 291 



3. Discontinuous Mutation Involving Virulence 292 



G. Interpretation of Influenza Virus Recombination 293 



1. Genetic Aspects 294 



2. The Bearing of Genetic Findings on the Nature of Influenza Virus 



Multiplication 297 



V. Genetic Interaction in other Virus Groups 299 



A. Recombination with Vaccinia and Rabbitpox Strains 299 



B. Interactions among Intestinal Viruses 301 



C. Genetic Literaction with Psittacosis Virus 302 



D. The Berry-Dedrick Phenomenon — Transformation of Shope Fibroma 



Virus to Myxoma Virus 302 



References 3 5 



Introduction 



One way of looking at virus infection is to picture it as the intrusion of one 

 genetic system (the virus) into the domain of another (the host cell) and the 

 subsequent interactions of the two systems at various levels. An essential part 

 of this concept is that of the eclipse phase during which the virus particle 

 disappears as an individual and is represented, operationally speaking, 



275 



