::i I PHYSIOLOGICAL GENETICS 



all located in the same section of chromosome III: bithorax, 

 58.7; bithoraxoid, .")'.». ."j; aristapedia, 58.5; proboscipedia, 45.7; 

 tetraptera, 51.34(?). 



Though not complete, this list of facts seems to be a formidable 

 (me All points taken together suggest strongly that the 

 chromosome is the actual hereditary unit controlling the develop- 

 ment of the Wild type that purely steric changes at the individual 

 point- of its length produce deviations from Wild type which 

 may he described as imitations, even as point mutations, though 

 no actual Wild-type allelomorph and therefore no gene exists. 



If such a view, which we consider to be tomorrow's theory of 

 the germ plasm, should turn out to be unavoidable, a number 

 of problems will have to be solved. The first one is whether or 

 not a model of such a chain molecule is available and whether or 

 not it is possible that the different points in its length exercise a 

 different specific, and independent catalytic action. It seems 

 that the most recent work of Bergmann and coll. (1937) on the 

 structure of the protein molecule has furnished such a model 

 (Goldschmidt, in press). It will be found to be nearly related 

 to the other models, especially that of Wrinch, with the advantage 

 of not using the conception of the gene any more. 



Bergmann starts from certain facts upon which he builds a 

 chemical hypothesis, and both facts as well as hypothesis appear 

 very helpful for our present purposes. The protein molecule is 

 known to consist of a chain of amino acid residues linked by 

 peptide bonds. According to Bergmann these residues are 

 arranged in a simple order. Each amino acid has its own rhythm 

 different from that of the others, and the superposition of all 

 these rhythms produces the pattern of the molecule. The 

 rhythm itself, meaning that one type of residue appears always 

 separated by a definite number of others in the chain, follows a 

 simple arithmetical rule. Thus silk fibroin which contains 

 glycine, alanine and tyrosine residues shows an arrangement of 

 these in the rhythm: 



G-A-G-X-G-A-G-X-G-A-G-T-G-A-G-X-G-A-G-X-G-A-G-X- 

 G-A-G-T-G (G-G = 2, A-A = 4, T-T = 16) 



The total number of members of a chain is 288 or a multiple 

 thereof. To organize such a molecule, a chemical organizer is 

 needed of immense specificity. According to Bergmann the 



