352 



ERWIN CHARGAFF 



TABLE V 

 Distribution of Purines and Pyrimidines in Deoxyribonucleic 



Acids from Different Organs of Four Mammalian Genera* 



Proportions in moles of nitrogenous constituent per 100 g. -atoms of 



phosphorus in hydrolysate, corrected for a 100% recovery, 



with their standard errors. 



Genus Organ 



Ox 



Sheep 



Pig 



Man 



Thymus 

 Liver 



Thymus 

 Liver 



Thymus 

 Liver 

 Spleen 

 Thyroid 



Thymus 

 Liver 



Average 



total 

 recovery 

 Mole % 



93.3 

 94.1 



94.3 

 89.9 



93.9 

 95.3 

 96.0 

 97.4 



94.6 

 95.4 



Ratio of 



adenine -|- 



thymine to 



guanine + 



cytosine 



1.36 

 1.37 



1.36 

 1.41 



1.43 

 1.44 

 1.43 

 1.41 



1.52 

 1.54 



• Taken from E. Chargaff and R. Lipshitz, J. Am. Chem. Soc. 75, 3658 (1953). 



pointing to the information collected in tabular "form in this section, a de- 

 cision whether different tissues of the same host yield identical or different 

 nucleic acid specimens is more difficult and will, perhaps, not be definite 

 before the analytical studies can be supplemented by other tests, for in- 

 stance, a completely reproducible fractionation process. For the moment, 

 it would appear that differences in the composition of preparations from 

 different organs, if they exist at all, are of very doubtful significance, al- 

 though some contrary findings have been reported following the administra- 

 tion of steroid sex hormones.-^* 



The results of a comparative study of the composition of many prepara- 

 tions from different organs of ox, sheep, pig, and man'" are summarized in 

 Tables V and VI. In no case were significant differences in composition 

 found when the deoxyribonucleic acids isolated from the thymus and liver 

 of the same genus were compared statistically, nor were differences found 

 between human normal and carcinomatous liver. In Table VI the signifi- 

 cance of differences between different genera is considered. It will be seen 



2" N. L Gold and S. H. Sturgis, J. Biol. Chem. 206, 51 (1954). 



