308 Action of the Genetic Material 



lie in the alteration of the normal relations between the synthesis of 

 RNA in the nucleus and that in the cytoplasm. The foreign nucleus 

 prevents the passage from the nucleus of the substances which control 

 the synthesis of the cytoplasmic RNA protein granules. Thus it is 

 concluded that the nucleus controls the synthesis of the microsomes, 

 which are the true agents of protein synthesis. Other evidence, such 

 as the quicker uptake of tagged amino acids in the microsomes and 

 the continuation of protein synthesis in enucleated cells, is in favor 

 of the conclusion. 



The problems regarding intranuclear and cytoplasmic synthesis 

 of RNA and the question of what passes through the nuclear mem- 

 brane have found diflFerent answers. Very interesting in this respect 

 are data from Brachet's school (Brachet and Chantrenne, 1952; 

 Vanderhaeghe, 1952) on Acetabularia, the object of HammerHng's 

 work, studied previously. The nucleolus is very rich in RNA and most 

 of the RNA is found in the rhizoma near the nucleus. In the non- 

 nucleated stem there is a gradient away from the nucleus. By tagging 

 proteins it is found (in agreement with Hammerling) that protein 

 synthesis is kept up in the enucleated fragment for a long time at a 

 high rate, which shows that the nuclear control of it is a remote one. 

 Stick and Hammerhng (1953) found that protein synthesis in the 

 cytoplasm is more or less independent of the nucleus. The reason 

 might be the presence of chloroplasts. I wonder whether the decisive 

 point is not the large mass of cytoplasm relative to the nucleus, just as 

 in large egg cells, with the result that the functions of the nucleus 

 are delegated to the cytoplasm in early stages of development, by 

 predetermination. In a single cell with much less cytoplasm, relatively 

 speaking, Amoeba proteus, Mazia and Prescott ( 1955 ) find that protein 

 synthesis, studied with tagged atoms, is wholly controlled by the 

 nucleus. I expect that all intermediate conditions will be found in 

 different materials. 



At this point the relation of the nucleus to the mitochondria also 

 is considered. The respiratory enzymes are attached to the latter; but 

 the mitochondria turn out to be less dependent upon the nucleus 

 than the microsomes. However, work by Mazia and Hirshfield (1951) 

 and others indicates that the nucleus produces a coenzyme for the 

 coupling of phosphorylations and oxidations in the mitochondria. 

 The relation to RNA is established by Marshak (1950), who showed 

 that RNA from nuclei contains more adenine than cytoplasmic RNA 

 does. If nuclear RNA is a precursor to cytoplasmic RNA, a liberation 

 of adenine must take place in the formation of the latter which might 



