102 Nature of the Genetic Material 



definite bonds setting free a reactive radical. A new residue may be 

 attached from the surroundings and thus the whole molecule may be 

 changed. From this it follows that the gene itself must be represented 

 by such an invisible atomic combination or molecule. 



Do these facts and deliberations by Delbriick now prove that 

 there is a definite, corpuscular gene (and the chromosome a gene 

 string) and that this gene is a single molecule? There are many 

 reasons why such a conclusion cannot be considered as established. 

 Delbriick realized that the same reasoning could also apply to any 

 other compound which, if stable, consists in the end also of atomic 

 assemblies to which, on whatever level of complication, the same 

 reasoning applies. Delbriick's analysis would also fit a concept of the 

 nature of the genie material of the type we are going to develop. 

 Timof eeff and Zimmer ( 1947 ) , realizing this, are more cautious in 

 their latest discussion, though basically they seem still in agreement 

 with the former conclusions. They state that the gene or at least its 

 important part must represent a physicochemical unit, a large mole- 

 cule, a micelle, an autonomous part of a micelle, or a unified, delimited 

 crystalline structure. But they add that it cannot yet be decided 

 whether the gene is an essentially autonomous, large molecule, for 

 example, a link in a chain of such strung-together molecules; or a 

 delimited and largely autonomous part of a micelle; or even a more or 

 less complicated micelle as a part of a compound structure made up 

 of many concentrated micelles (which would be identical with a 

 whole chromosome). The decisive point for our present discussion is 

 that the most recently reported group of facts and analyses do not 

 prove or even make probable that the gene is a solitary, single mole- 

 cule, even in the opinion of those who developed the concept. 



It should be added that the facts upon which the foregoing 

 analysis was based are in no way uncontested. The Treffer theory, 

 which plays such a great role here and which is accepted also by Lea 

 (1947) and Lea and Catcheside (1945), has been under fire for a 

 long time. Numerous reasons have been given why the biological 

 action of radiations cannot be so simple, and it looks as if the ingenious 

 theory were being abandoned by the specialists. This applies to the 

 Treffer theory as such, as originally conceived by Dessauer (see 1954), 

 as well as to its application to genetic change. A considerable part of 

 the criticism is based upon the facts of chemical mutagenesis, which 

 are difficult to understand in terms of this theory. A major criticism is 

 derived from the discoveries of Stone and his school (see 1947, 1948, 



