Heterogeneity of Deoxyribonucleic Acid (DNA) 10 



exchanger containing carboxymethyl groups attached to the cellulose 

 was without any affinity for calf-thymus DNA at neutral pH. How- 

 ever, one containing the basic diethylaminoethyl group removed DNA 

 from solution, and fractions could be obtained by salt elution. A new 

 anion exchanger, Ecteola-Cellulose, prepared by the treatment of alka- 

 line cellulose with a mixture of epichlorohydrin and triethanolamine, 17 

 has given the most provocative results. A diagram of the chromato- 

 graphic behavior of highly polymerized calf-thymus DNA on a column 

 of this anion exchanger is shown in Fig. 1. Many chromatographic 

 fractions of DNA were obtained by continuous gradient elution with 

 NaCl solution of increasing concentration followed by graded changes 

 in ?)H. About 65% of the original DNA was recovered at neutrality, 

 some 20% up to pH 9.9, and the remainder required strong alkali for 

 complete removal. Analogous chromatographic patterns result from 

 the application of a discontinuous salt concentration or pH gradient. 



Fractions of DNA obtained this way are non-dialyzable and retain 

 their chromatographic properties on rechromatography ; the reproduci- 

 bility of the patterns is indeed gratifying. 



With this method at hand, a solution of transforming DNA from 

 pneumococcus * was passed through a column of Ecteola-Cellulose and 

 all of the transforming activity as well as of the DNA was retained 

 by the exchanger. Fractions of DNA exhibiting transforming activity 

 were obtained at several places along the chromatogram following the 

 elution; wherever the activity was detected it always coincided with 

 the presence of DNA. Perhaps this can be taken as additional argu- 

 ment that DNA can carry and transmit genetic information. At any 

 rate, retention of biological (transforming) activity following its re- 

 moval from solution by the exchanger and its subsequent elution indi- 

 cates that little tampering with the integrity of the DNA preparation 

 had resulted. 



The pneumococcal DNA preparation originally possessed four de- 

 monstrable genetic properties; these included transformations to peni- 

 cillin, streptomycin and sulfonamide resistance, and mannitol utiliza- 

 tion. 18 The DNA preparation, isolated from bacteria arising from a 

 single clone, induced these heritable transformations at random essen- 

 tially as single, independent events. However, a significant number 

 of the mutant cells showed two properties, those of mannitol utilization 

 and of streptomycin resistance which were acquired, not at random, 

 but rather as related or connected events. 18 It would appear, then, 



* Unpublished experiments, with S. Beiser, J. K. Fresco, and R. D. Hotchkiss. 



