DEOXYPENTOSE NUCLEIC ACIDS 



13 



TABLE 4 



COMPOSITION OF TWO MICROBIAL DEOXYRIBONUCLEIC ACIDS 



was isolated. This procedure assumes that there is no organ 

 specificity with respect to the composition of deoxypentose 

 nucleic acids of the same species. That this appears indeed to 

 be the case may be gathered from Tables 2 and 3 and even better 

 from Table 6 where the average purine and pyrimidine ratios in 

 individual tissues of the same species are compared. That the 

 isolation of nucleic acids did not entail an appreciable fraction- 

 ation is shown by the finding that when whole defatted human 

 spermatozoa, after being washed with cold 10% trichloroacetic 

 acid, were analyzed, the same ratios of adenine to guanine and 

 of thymine to cytosine were found as are reported in Tables 5 

 and 6. It should also be mentioned that all preparations, with 

 the exception of those from human liver, were derived from 

 pooled starting material representing a number, and in the case 

 of human spermatozoa a very large number, of individuals. 



The deoxypentose nucleic acids extracted from different 

 species thus appear to be different substances or mixtures of 

 closely related substances of a composition constant for different 

 organs of the same species and characteristic of the species. 



The results serve to disprove the tetranucleotide hypothesis. 

 It is, however, noteworthy — whether this is more than accidental, 

 cannot yet be said — that in all deoxypentose nucleic acids 

 examined thus far the molar ratios of total purines to total 

 pyrimidines, and also of adenine to thymine and of guanine to 

 cytosine, were not far from 1 . 



References p. 23 



