Fig. 9. Method for Determining Sequences in 

 DNA. 



\>B 



SYNTHESIS 



(by polymerase) 



(by micrococcal 

 DNase and splenic 

 diesterase) 



2) The pattern of relative frequencies of the sequences is unique and re- 

 producible in each case and is not readily predicted from the base compo- 

 sition of the DNA. 



3) Enzymatic replication involves base pairing of adenine to thymine and 

 guanine to cytosine and, most significantly: 



4) The frequencies also indicate clearly that the enzymatic replication 

 produces two strands of opposite direction, as predicted by the Watson and 

 Crick model. 



These studies and anticipated extensions of them should yield the dinucleo- 

 tide frequencies of any DNA sample which can serve as an effective primer 

 for enzymatic replication and thus provide some clues for deciphering the 

 DNA code. Unfortunately this method does not provide information about 

 trinucleotide frequencies but we are hopeful that with the improvement of 

 enzymatic tools for analysis and chromatographic techniques for isolation 

 some start can be made in this direction. 



Requirement for four triphosphates and DNA for DNA synthesis. 



Returning to the earlier-stated requirement for all four deoxynucleoside 

 triphosphates and DNA in order to obtain DNA synthesis, we can now regard 

 and understand these requirements as another and final line of evidence for 

 hydrogen bonding. Without added DNA there is no template for hydrogen 

 bonding and without all four triphosphates synthesis stops early and abruptly 

 for lack of a hydrogen bonding mate for one of the bases in the template. 



s-72 



