Genie and Non-genic Parts of the Chromosome 51 



molecular stiucture into that of the intruder. Since genie material 

 is self-reproducing, the last assumption is not very commendable; 

 and the first one appears at present beyond the limit of what we can 

 safely believe. The geneticist who approaches these facts with an 

 open mind will be loath to accept such an explanation as final and 

 to consider transformation a proof of the nucleic acid nature of the 

 genie material. He will expect that further work may lead to a more 

 plausible explanation. 



If the idea promoted by some chemists is true — that the nucleic 

 acids are not themselves self-reproducing units but act as templates 

 or scaffolds which keep the self-duplicating protein molecules in 

 place and shape during this process — one corollary would be that 

 the nucleic acids are synthesized and augmented outside the chromo- 

 somes and become attached to the protein chain secondarily by for- 

 mation of salt links. The action of the transforming DNA extract 

 could then mean that the rich source of DNA offered in the extract 

 is not used via breakage and resynthesis of the molecule but enters 

 as such into the bacterial nucleus, where at the time of chromosomal 

 growth and division it replaces similar molecules simply by being 

 available in larger quantities. Transformation, then, would introduce 

 somewhat different templates; this means that DNA is not the genie 

 material but one indispensable for the reproduction of genie material. 

 Though not too satisfactory in detail, such a type of interpretation 

 may open the way for a different experimental attack. 



The new model of the DNA molecule proposed by Watson and 

 Crick (see I 2 B b bb) may support such an interpretation or a 

 similar one. The self-duplication of the two haff-molecules proposed 

 by these authors takes place by the addition of nucleotide monomeres 

 which are assumed to be plentiful in the surroundings. In the adapta- 

 tion experiment there might be available within the organism many 

 times more of the introduced and depolymerized DNA than the 

 amount of the available genuine DNA monomeres synthesized in the 

 bacterial cell. Just as tagged atoms are built into the molecules of 

 different kinds in organisms, these introduced monomeres could be 

 built into the duplicates of the half-molecules. Since this would 

 happen in subsequent duplications in a compound-interest sequence, 

 the new DNA would soon replace the old one completely. Whether 

 this applies to the entire polymere or only to definite macromeres 

 needed for the mutant character cannot be decided, though the 

 result would be the same in either case. (The fact that in vitro 

 depolymerized DNA does not produce transformations may or may 



