Genie and Non-genic Parts of the Chromosome 45 



and stated, "The cytological diflFerence between the white mutant 

 and wild type, confirmed in this material, is thus not accompanied by 

 a quantitative difference in ultra-violet absorbing material," which 

 is DNA. This does not help us very much in our discussion. 



A completely different attack upon the same problem has been 

 made by analyzing the action of chemical mutagens. Clark (1953) 

 comes to the conclusion that pyronine produces its mutagenic effect 

 by combining directly with nucleic acid. He thinks there is a possi- 

 bility that the mutagenic action might result from combination with 

 depolymerized DNA during its synthesis. But he considers also the 

 possibility of primary action on RNA in the cytoplasm which is later 

 incorporated into the nucleus. Whatever these processes may be, they 

 could both be interpreted in favor of DNA as genie material or as a 

 template. In the first possibility, the combination with the dye would 

 produce alterations in the spatial arrangement of nucleotides charac- 

 teristic for a given locus. In the second, the chemical would prevent 

 the DNA from maintaining the protein in the expanded state (the 

 scaffolding function). This type of attack on our problem ends again 

 in a non liquet. 



The geneticist, taking cognizance of this group of facts, can 

 hardly doubt that DNA must play an important role in the makeup 

 of the genie material. This, however, does not necessarily mean that 

 it is the genie material. The chemical extraction of a few proteins 

 from the chromosome does not convey much information on the 

 actual chemical composition of the continuous chromonema to which 

 the DNA seems to be attached by salt links in identically spaced 

 groups (Astbury, 1939). If we are looking for individual genes, the 

 molecules of DNA may be the answer, though it raises all the prob- 

 lems just discussed. However, if we abandon the idea of the corpuscu- 

 lar gene, it appears more probable that the genie action resides in the 

 combination of the proteinic chromonema with the attached DNA, 

 and many facts to be discussed still favor such a view. But it will 

 be good to realize how much semantics is involved in this discussion. 

 If the DNA is the necessary scaffolding for the duplication of protein 

 molecules and therefore must be kept constant in quantity, spacing, 

 and so on in order to act specifically, we might call it the primary 

 genetic material, even if it were not the active one, or we might call 

 it the auxiliary to the genuine one; or we might stress the inter- 

 dependence of the two, as I prefer to do. 



At the end of this discussion a fact should be mentioned briefly 

 to which we shall return below when discussing the theory of the 



