142 NUCLEOTIDE SEQUENCE IN DEOXYRIBONUCLEIC ACIDS 



during hydrolysis exceeded that of deoxycytidine 3 ',5 '-diphos- 

 phate: this indicated the occurrence of larger quantities of soUtary 

 thymine than cytosine, but the ratios of the soHtary residues were 

 not those that would have been predicted statistically from the 

 total abundance of these pyrimidines in the polymers. In the 

 nucleic acid of the GC type an inversion in the rates of liberation 

 of the nucleoside diphosphates is observed, as expected; but in 

 this instance, the ratios of sohtary and of total pyrimidines are 

 not widely different: 0.59 v^-. 0.52. 



TABLE 3 1 



DIFFERENTIAL DISTRIBUTION ANALYSIS OF DEOXYRIBONUCLEIC ACID OF BCG* 



T C CC 



Total pyrimidine, as mole % P 16.7 32.3 



Solitary pyrimidine, as mole % of total 



constituent in DNA 13.6 12.0 



Solitary or bunched pyrimidines, as 



mole % P 2.27 3.88 1.13 



Total T/C, molar ratio 0.52 



Solitary T/C, molar ratio 0.59 



* The figures are taken from a previous paper^o. CC designates dicytidine 

 triphosphate. Compare Table 28 for other explanations. 



/. Nucleotide arrangement in the deoxyribonucleic acid of E. coli 

 grown in the absence and presence of 5-bromouracil 



The deoxyribonucleic acid of E. coli is unusual, being composed 

 of nearly equimolar proportions of the four nucleotide con- 

 stituents^' ^^ No obvious distinctions appear, even when different 

 variants and mutants are examined, although it is not unlikely 

 that a careful differential distribution analysis would reveal some 

 differences. Such a study has, however, not yet been undertaken. 

 It appeared of great interest to study the effect of a fraudulent 

 analogue on the sequence characteristics of a deoxyribonucleic 



