12 Nature of the Genetic Material 



participation in the formation) of the spindle fiber and, in special 

 cases, as in the Paludina sperm, an axial fiber. Therefore the cen- 

 tromere would not be different from the genie material if self- 

 duplication alone were considered to be the characteristic of genie 

 material. But it would be very different in regard to functional 

 potencies. It is important to keep this in mind when discussing self- 

 duphcation as the main characteristic of genetic material. There is a 

 whole school wilUng to call any self -duplicating material a gene. This 

 attitude forces the facts into a scheme which does violence to clear 

 notions. 



Returning to the phenomenon of chromosome division, another 

 point from Lwoff's work must be mentioned. At a given time of the 

 ciliate cycle, all kinetosomes may divide simultaneously. This means, 

 to Lwoff, the interaction of the kinetosome with a specific substance. 

 Applying this fact and interpretation to the chromosome, it could be 

 concluded that the appearance of such a hypothetical substance 

 within the chromosome ( all chromosomes ) would start the division of 

 all self-duplicating parts of the chromosome, centromere as well as 

 genie material. If this is so, the chromosome becomes a still more 

 complicated organism. In certain divisions (meiosis of the lepidopteran 

 egg) large amounts of RNA are sloughed off the chromosome, which 

 must have been present somewhere outside the chromonema itseff. 

 This underscores the danger of drawing conclusions about processes 

 on the chromosonial level from molecular models. 



Do these facts and interpretations shed light upon the division of 

 the chromosome as a whole? We see two possibilities. The first is that 

 no further problem is involved. Just as a kinetosome duplicates as a 

 whole, with an organization far above the molecular level, the much 

 more complicated chromosome may duplicate in all its parts and the 

 resulting daughter parts separate. This means that the old naive 

 description of the chromosome being spht in two is literally true, with 

 the addition that some essential parts are self-duplicating after the 

 manner required by the template theory. This leaves us where we 

 were, unable to understand such a procedure in a micellar, fibrous 

 body only part of which, the genie material (and perhaps also the 

 centromere), is supposed to be self-duplicating on the molecular level. 



The second possibility is that we do not compare the chromosome 

 to the kinetosome or to a string of kinetosomes but to the entire 

 protozoan organism, of course only by analogy, not by homology. 

 We consider the chromosome as a unit containing systems of self- 

 duplicating subunits, arranged according to a pattern under the in- 



