BIOLOGICAL ORDER 



1. The prophage is the genetic material of the bacteriophage. It 

 carries the information for the production of bacteriophage particles. 



2. There is only one prophage per bacterial chromosome. 



3. A given prophage is always attached to the same site, or locus, 

 of the bacterial chromosome. 



The receptor. That a given prophage is able to reach and recog- 

 nize a specific chromosomal site is something strange. 



Cytologists know that during a certain phase of the maturation 

 of the sexual cells, a pairing of homologous chromosomes takes place. 

 The two chromosomes stick to each other at their homologous 

 regions. The nature of the forces that intervene in the process is 

 unknown. In any event, it is admitted that the attachment of the 

 viral genetic material on a specific site of the bacterial chromosome 

 is the consequence of a correspondence of structure of the two 

 interacting nucleic acids: the bacterial one and the viral one. This 

 correspondence, whether it is homologous or complementary, is in 

 favor of the hypothesis according to which the genetic material of 

 the phage has, long ago, originated from the bacterial chromosome. 



Prophage and vegetative phage. When, after an infection, the 

 genetic material of the bacteriophage has attached itself to the 

 bacterial chromosome, the bacterium is lysogenic. The genetic mate- 

 rial of the bacteriophage, the prophage, behaves differently from 

 the vegetative genetic material. During the vegetative phase, the 

 viral chromosome multiplies at its own pace. It duplicates itself 

 every 2 or 3 minutes. The prophage duplicates itself alongside the 

 bacterial chromosome, that is, every 20 to 50 minutes, according to 

 the bacterial species, nature of the medium, temperature, etc. During 

 the vegetative phase, the phage chromosome is autonomous. In a 

 lysogenic bacterium, it is, as prophage, submitted to bacterial control. 

 How is it possible that one and the same structure exhibits such a 

 dual behavior? This is one of our problems. 



But there is another difference between vegetative phage and 

 prophage. The vegetative viral chromosome expresses its poten- 

 tialities: viral proteins are synthesized, and the vegetative phase 

 culminates with the organization of infectious particles. The pro- 

 phage does not express its potentialities: no viral proteins are to be 

 found in a lysogenic bacterium and of course no infectious particles. 



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