8o ERWIN CHARGAFF 



TABLE IV 

 Differential Distribution Analysis of Deoxyribonucleic Acid of BCG* 



* The figures are taken from a previous paper [40]. [CC] designates dicytidine 

 triphosphate. Compare Table I for other explanations. 



one in which guanine and cytosine preponderated. We first discovered 

 this type in tubercle bacilli [24] ; but it has since that time been found in 

 many micro-organisms [7, 41]. The distribution analysis of the deoxy- 

 ribonucleic acid of an avirulent variant (BGC) of bovine tubercle bacilli 

 is shown in Table IV. In the nucleic acids of the AT type, as was shown 

 before, the quantity of thymidine 3', 5 '-diphosphate released during 

 hydrolysis exceeded that of deoxycytidine 3',5'-diphosphate: this indi- 

 cated the occurrence of larger quantities of solitary thymine than cytosine ; 

 but the ratios of the solitary 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 solitary and of total pyrimidines are not 

 widely different: 0-59 vs. 0-52. 



NUCLEOTIDE ARRANGEMENT IN THE DEOXYRIBONUCLEIC ACID OF E. CoU 

 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 constituents [7, 41]. 

 No obvious distinctions appear, even when different variants and mutants 

 are examined, although it is not unlikely that a careful differential distribu- 

 tion analysis would reveal some differences. Such a study has, however, 

 not yet been undertaken. 



We have as a first approach to the problem of the effect of a mutagenic 

 agent on the sequence characteristics of a deoxyribonucleic acid, investiga- 

 ted the nucleic acid produced by a thymine auxotroph of E. coli, grown in 



