IV. THE NATURE OF THE GENE 



The existence of the Wild-type gene, as previously mentioned, 



is assumed only on the basis of the mutant genes. Whatever 

 conclusions upon the nature of the genes are drawn from experi- 

 mental facts, in the end they must be derived from views regard- 

 ing the process of mutation. We do not intend to quote every 

 single utterance regarding the nature of the gene, as almost all 

 geneticists have expressed their views at some time more or less 

 completely. We shall report only such theories as have been 

 derived from a large body of facts and which have been tested 

 more or less thoroughly. 



There are a few a priori considerations regarding the nature 

 of the gene which have been emphasized in a more or less similar 

 way by a majority of the workers in this field (e.g., see Hagedoorn, 

 1911; Troland, 1917; Goldschmidt, 19205; Muller, 1922; Plunkett, 

 1926; Wright, 1925; Koltzoff, 1928; Mittasch, 1935; Schmalfuss 

 et al., 1928/f.). A gene is supposed to have the following 

 characteristics : 



1. It is a highly active substance, and it is potent in very small 

 quantities. 



2. The substance of the gene is doubled before each cell 

 division; it is therefore capable of assimilation and grow r th. 



3. The gene is able to undergo a definite, sudden, and in many 

 cases reversible change, called mutation. 



4. The mutated gene is perpetuated in the same way, is as 

 stable as the original gene, up to the moment of another mutation. 



The first two points are accounted for best by the assumption 

 that the gene has the chemical properties of a catalyst (including 

 enzymes) and more specifically of an autocatalyst, which repro- 

 duces itself as one of the end products of the catalyzed reaction. 

 Hagedoorn (1911) was the first to elaborate this idea, which has 

 since reappeared more or less independently in the writings of the 

 authors quoted above. This interpretation of the gene, which 

 defines only its type of action in terms of chemical kinetics, is 

 independent of all the special ideas that have been elaborated to 



282 



