10 



Replication of 



Genetic Material in 



Microorganisms 



Maintenance of genetic continuity in a clonal line of cells depends on 

 the successful accomplishment of two processes: (1) reasonably faithful 

 replication of the genetic information, and (2) rather precise distribution 

 of the products of replication to daughter cells. While it is generally 

 assumed that these processes are carried out in essentially the same 

 fashion by all living things, this may not necessarily be so. If it is true, as 

 it appears to be, that genetic information is encoded in nucleic acid 

 chains in all organisms including viruses, then the presumption that the 

 basic mechanism of replication is universally the same is probably jus- 

 tified. Just what this mechanism may be is not yet known, although a 

 number of hypotheses have been proposed (Delbruck and Stent, 1957). 

 Most of these assume validity for the Watson-Crick model of DNA 

 structure as an entwined duplex of complementary strands (Figure 2-5). 

 Basically there seem to be three possible situations: (1) where the pa- 

 rental duplex direcdy or indirectly serves as a template for a daughter 

 duplex, (2) where the chains of a duplex are separated so that each 

 daughter complex consists of one old and one new chain, and (3) where 

 the original parental material is distributed through the four chains of 

 the daughter duplexes. Theoretically, the answer to the question of mech- 

 anism may emerge from genetic and biochemical analyses of replication 



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