236 FINE-STRUCTURE OF PROTOPLASM 



II 



It will be clear from the following that a similar comparison applies 

 to other enzymes, at any rate so far as the prosthetic group is con- 

 cerned : 



Co-enzyme of carboxylase (aneurinopyrophosphoric acid) 44 atoms 



Co-enzyme of the dehydrogenase II (nucleotide of nico- 

 tinic acid + phosphoric acid + nucleotide of adenine) 

 hydrogenated -^ 7^ ,, 



Co-enzyme of the yellow respiratory enzyme (lactoflavin- 



dinucleotide of adenosine) 81 ,, 



Average target area of the genes 1000 ,, 



The apo-enzymes of these desmoenzymes are not freely moving 

 colloidal particles; Hke the genes in the chromosome, they are em- 

 bedded in the submicroscopic cytoplasmic structure. Only by auto- 

 lysis can they be liberated under certain circumstances and made 

 accessible to examination. 



The comparison between gene and enzyme may not be merely a 

 superficial one ; one might at least try to probe further. It is scarcely 

 to be wondered at that the gene and target area should be so much 

 larger than the volume of the apo- and co-enzymes, if it be remem- 

 bered how much more complicated than single metabolic reactions 

 are the processes of development controlled by the genes. Latterly it 

 has become ever more evident that this control is exercised chemically. 

 When a mutation takes place, these chemical processes proceed 

 differently. It is therefore not wrong to assume that the target area 

 acts like the prosthetic group of an enzyme and that the controlled 

 processes follow a different course owing to changes in this sensitive 

 area. As this area contains approximately 1000 atoms, 50 amino acid 

 residues (with on an average 20 atoms) are located in it, allowing 

 protein chemistry to come into full play in its almost unlimited variety. 



According to the hypothesis propounded here, the gene would, in 

 the terminology of Haase-Bessel(i936), consist of a carrier (pheron) 

 and chemically active regions (agon), some idea of the dimensions of 

 which can be formed on the basis of the target theory. Since, however, 

 every colloidal particle of the apo-enzyme carries only one amicro- 

 scopic operative group, this conformity probably cannot be assigned 

 to the genes. There are, maybe, several chemically active regions in 

 the large disc of Fig. i26e. This would explain polyphaeny, i.e., that 



