260 



PHYSIOLOGY OF BACTERIA 



protein molecules. It seems permissable to assume that 

 the molecules of which the chromosomes are composed, 

 are of the same order of magnitude as the genes, and that 

 a gene consists of only a few very large molecules, perhaps 

 only of one. 



Table 73. — Size of Various Protein Molecules Calculated from 

 Sedimentation Velocity Measurements 



Protein 



Molecular 

 radius in m/i 



Bence- Jones* 



Egg Albumin* 



Insulin* 



Hemoglobin 



Serum Albumin 



Serum Globulin 



Casein 2X 



Amandin* 



Edestin* 



Excelsin* 



Legumin* 



Phycocyan 



Phycoery thrin * 



Casein 4X 



Hemocyanin (Limulus). 

 Hemocyanin (Helix)*.. 



3.94 

 3.94 

 3.96 

 3.96 

 3.94 

 3.95 

 4.18 

 6.96 

 12.00 



* Molecules nearly spherical. 



The enzymes of dissimilation can be produced by the 

 cell; a cell can control its enzyme content to a certain 

 degree (p. 131). It seems, however, that a gene can be 

 produced only by another gene of the same kind. If a 

 gene is destroyed, the cell cannot usually replace it, 

 and if such a cell can divide at all, the two daughter cells 

 will lack this gene and will be abnormal. More com- 

 monly, the cell will not divide. 



Chromosomes have never been observed in bacteria. There is 

 some indirect evidence for their existence, however. Lacassagne 



