THE CYTOPLASM 



breaks down as soon as it is formed so that the concentration at 

 equihbrium is so low as to be indetectable by the fermentation it 

 causes. 

 When mehbiose is added, the concentration of enzyme rapidly 



SACCHAROMYCES 

 CARLSBERGENSIS CEREVISI/E 



P 



n 



NO MELIBIOSE 



IN 



SUBSTRATE 



MELIBIOSE 

 RESTORED 



Fig. 43. — The inheritance of the capacity to ferment mehbiose in yeast crosses 

 according to Lindegrcn and Spiegehiian (1944). The plasmagene responsible depends 

 on the action of a nuclear gene for its origin, while for its survival in the absence of 

 the nuclear gene it depends on the presence of mehbiose in the substrate. 



grows; so rapidly that it cannot be due to the mere accumulation 

 of the output from the nucleus by removal of the counter-balancing 

 destructive process. On the contrary the enzyme, or precursor, in 

 the cytoplasm must take on the self-propagating properties of a 

 plasmagene when mehbiose is added. The mehbiose itself conditions 

 the plasmagenic properties of the enzyme which ferments it. 



180 



