300 PHYSIOLOGICAL GENETICS 



upon their action without any other change. His model is two 

 molecules with side chains of opposite activity, which when very 

 near together mighl neutralize each other though not if distant. 

 This would be a model for what is called now the position effect, 

 which also indicates that individual genes are not independent 

 from one another. ( Details will be discussed later.) 



A. The Gene as a Side Chain of a Molecule 



Actually, theories of the gene have been conceived thai regard 

 the gene only as a part of a whole. Repeatedly geneticists have 

 declared that they consider the chromosome itself as a giant 

 molecule, the side chains of which represent the genes (Castle, 

 1919; Renner, 1920). Koltzoff (1928) has elaborated this idea. 

 To him (as to many geneticists) the chromatic part of the 

 chromosome means nothing but a substratum which surrounds 

 the essential part of the chromosome, a chromatic thread repre- 

 senting the gene string of other authors. This is either a very 

 long protein molecule or a bundle of such molecules around which 

 new molecules are assimilated from the surrounding chromatin 

 mixture so that the bundles grow and may divide. In these long 

 molecules, the many different radicals have their definite position, 

 and all chemical changes in these radicals, e.g., removal of one 

 or the other atom or replacement by another residue, will appear 

 as a mutation. 



It is obvious that this view does not make it easier to under- 

 stand genie action. Its importance is that it constitutes a first 

 step toward a definition of the gene as a part and not as an 

 independent unit. 



Koltzoff (1934, 1935) has repeatedly returned to his ideas and 

 modernized them. He compares (page 293) the recent develop- 

 ments in chemistry with his views and brings them in line. The 

 chromonema or gene string or genonema is a chain molecule (or 

 micella composed of such molecules) containing protein and other 

 radicals, the genes. From the surrounding solution these radicals 

 attract their like and synthesize them, assimilate them. The 

 surplus of assimilated molecules, i.e., the genes, their parts, or 

 complexes, pass into the cytoplasm, and thus the genes produce 

 their effects. Complicated and necessary substances like sterols 

 and agglutinins are also supposed to be actually present as genes, 

 which assimilate their like. It may be added that more specific 



