32 NUCLEIC ACIDS AS CELL CONSTITUENTS 



course of which many less suitable or less stable components 

 must have been eliminated. One could speak of the survival of 

 the fittest nucleic acids. Such macromolecules will exhibit diver- 

 sity and uniformity at the same time, since they are called upon 

 to perform, in diverse species, the same tasks. It is, therefore, 

 perhaps not astonishing that the nucleic acids will share certain 

 features that may be directly connected with their stability or 

 their ability to form conjugated nucleoproteins. One property 

 which is quite striking is the uniform absorption spectrum in the 

 ultraviolet of all highly polymerized DNA specimens, both with 

 respect to the position and the intensity of the absorption 

 maximum. The center of absorption fluctuates only between 257 

 and 261 m/i and the (e) P is around 6600. Another surprising 

 feature is the balance between amino groups and enolic hydroxyls 

 in all DNA preparations examined by us. (See last column of 

 Table 13.) Even in the core preparations, this ratio changed 

 only very little. 



But let us return for a moment to the other outstanding char- 

 acteristic of nucleic acids, viz., their diversity. If we accept the 

 evidence of the existence of species-specific DNA, then there 

 arise many new questions, both of a biological and chemical 

 nature. DNA presumably is an important part of the chro- 

 mosomes and may be surmised to be involved in their biological 

 functions. Does this mean that a cell contains as many different 

 DNA individuals as it contains genes? Or can one and the same 

 species-specific DNA form so many three-dimensional structures, 

 in connection with the proteins to which it is attached, that the 

 genie requirements are fulfilled? (For a more detailed discussion 

 of some of these points, cf. Ref. 31.) This question, as so many 

 others in this field, cannot yet be answered. No way has as yet 

 been found to fractionate a family of very similar macromolecules 

 which may differ in no more than the sequence of a few of their 

 component nucleotides. But one could perhaps say that the more 

 regular the arrangement of nucleotides is in a given DNA, the 

 less the chance of its forming many different specific structures. 

 And this brings us again to the very important question of 



