THE PROBLEM OF NUCLEOTIDE SEQUENCE IN DEOXYRIBONUCLEIC ACIDS 75 



mechanism will, however, have to await a better understanding of the fate 

 of the free deoxyribose residues liberated in the initial stage of the removal 

 of purines by acid. 



NUCLEOTIDE ARRANGEMENT IN ANALYTICALLY INDISTINGUISHABLE DEOXY- 

 RIBONUCLEIC ACIDS OF DIFFERENT CELLULAR ORIGIN 



It happens quite often that deoxyribonucleic acids of taxonomically 

 entirely different origin exhibit identity of composition as regards the 



TABLE I 



Differential Distribution Analysis 

 OF Three Otherwise Indistinguishable Deoxyribonucleic Acid Preparations* 



Source: Ox Man Arbacia lixula 



DNA fraction: (0-75 m) (i -o m) (2-6 m) 



T C [TC] T C [TC] T C [TC] 



Total 



pyrimidine, 



as mole "„ P 299 200 29-9 19-8 30-9 196 



Solitary 



pyrimidine, 



as mole "o of 



total constituent 



in DNA 15-9 92 19-9 63 160 140 



Solitary or 

 bunched 

 pyriiTiidines, as 

 mole % P 4-75 1-^4 I '72 5 '95 1-25. 1-71 4 '94 2-74 i-66 



Total T/C, 



molar ratio 1-50 1-51 i"58 



Solitary T/C, 



molar ratio 2-58 4 '76 i ■ So 



* The figures are taken from previous papers [21, 36]. The deoxyribonucleic 

 acid fractions are described by the molarity of NaCl employed for the dissociation 

 of the histone nucleate [9]. T designates thymine or thymidylic acid, C cytosine 

 or deoxycytidylic acid, [TC] the two isomeric dinucleoside triphosphates com- 

 prising cytidine and thymidine (reported as moles of dinucleoside triphosphate 

 per 100 gm. atoms of nucleic acid phosphorus). 



distribution of the nitrogenous constituents. (Compare the example of the 

 deoxyribonucleic acids of the sheep and the salmon cited previously [i6]). 

 In such cases, the method of differential distribution analysis discussed in 



