Heterogeneity of Deoxyribonucleic Acid (DNA) 21 



that the preparation of DNA consisted, at least, of five DNA fractions 

 (or molecules); each of four of these was associated with just one 

 identifiable genetic property. Two of these properties appeared to 

 be linked together in the fifth species of DNA. 



The initial attempts to separate this pneumococcal DNA into frac- 

 tions of discrete activity were somewhat equivocal. The method 

 appears to have a high resolution. In consonance with the evidence 

 cited above, it supports the notion that DNA is highly heterogeneous. 

 It remains to be seen whether this heterogeneity of DNA will help 

 explain some of the pressing problems of biology. 



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