2!M) CHAPTER 21 



is lengthened slightl) ) or extensive (when essentially wholly-new strands arc produced). 

 Alter .1 lag period. /.. coli I)N A polymerase can synthesize dA I and dGdC <lc novo; 

 that is. m the absence of pre-existing DNA; call thymus DNA polymerase cannot 

 catalyze de novo DNA synthesis. 



Nearest-nucleotide-neighbor analysis reveals that complementary DNA strands are 

 synthesized in vitro in opposite directions, and that each type of natural DNA has 

 unique dinucleotide sequences not predictable from its base composition. Nucleotide 

 sequences, hence, do not occur at random in vivo, as strikingly exemplified in a "natural 

 dAT" DNA found in a crab. 



I he DNA product of an extensive synthesis in vitro closely resembles natural DNA 

 in primary and secondary structure and in other physical and chemical respects. Conse- 

 quently, this in vitro DNA synthesizing process is considered to be a biological process. 

 These results also support the Watson-Crick structure of chromosomal DNA and its 

 replication, after strand separation, through the formation of complementary strands. 



//; vitro, E. coli DNA polymerase is reported to use double-stranded RNA to syn- 

 thesize complementary double-stranded DNA without involving complete strand 

 separation. 



REFERENCES 



Berg. P.. Fancher. H.. and Chamberlin, M.. "The Synthesis of Mixed Polynucleotides 

 Containing Ribo- and Deoxyribonucleotides by Purified Preparations of DNA 

 Polvmerase from Escherichia coli," in Informational Macromolecules, Vogel, H. J., 

 Bryson, V.. and Lampen, J. O. (Eds.), New York: Academic Press, 1963, pp. 

 467-483. 



Bessman, M. J., "The Replication of DNA in Cell-Free Systems," Chap. 1, pp. 1-64, in 

 Molecular Genetics, Part I, Taylor, J. H. (Ed.), New York: Academic Press, 

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Bollum, F. J., " 'Primer' in DNA Polymerase Reactions," Progr. Nucleic Acid Res., 

 1:1-26. 1963. 



Bollum, F. J.. "Studies on the Nature of Calf Thymus DNA-Polymerase Products," 

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Burton. K., Lunt. M. R., Petersen, G. B., and Siebke, J. C, "Studies of Nucleotide 

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 26:27-34, 1964. 



Cavalieri, L. F., "Nucleic Acids and Information Transfer," J. Cell. Comp. Physiol., 

 62 (Suppl. 1 to No. 2) :1 11-122, 1963. 



Habermann. U.. Habermannova. S.. and Cerhova, M., "The Distribution of Nucleotides 

 into Pvrimidine and Purine Nucleotide Clusters in the Polynucleotide Chain of 

 DNA from Escherichia coli C," Biochim. Biophys. Acta. 76:310-311, 1963. 



Romberg. A.. Enzymatic Synthesis of DNA, New York: J. Wiley & Sons, 1962. 



Romberg. A.. Bertsch, L. L., Jackson. J. F.. and Rhorana. H. G., "Enzymatic Synthesis 



of Deoxyribonucleic Acid, XVI. Oligonucleotides as Templates and the Mechanism 

 o! Their Replication," Proc. Nat. Acad. Sci., U.S., 51:315-323. 1964. 



Krakow. J. S.. Kammen, H. O.. and Canellakis, E. S., "The Incorporation of Ribo- 

 nucleotides into Terminal Positions of Deoxyribonucleic Acid." Biochim. Biophys. 

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Lee-Huang, S.. and Cavalieri, L. F., "Polyribonucleotides as Templates for Polydeoxy- 

 ribonucleotides," Proc. Nat. Acad. Sci.. U.S.. 50:1116-1122, 1963. 



