Chapter 2 



The Role of Ribonucleic Acids in Growth 

 and Morphogenesis 



After a brief discussion of the possible part played by RNA in 

 fertilization and cleavage, we shall concentrate on the relationships 

 between RNA and primary morphogenesis, the accent being placed 

 on the induction of the nervous system by the organizer in am- 

 phibians. 



1. FERTILIZATION AND EARLY CLEAVAGE 



There is little evidence that RNA plays a direct role in the fertiliza- 

 tion of the egg. As we have already seen, ripe spermatozoa prob- 

 ably contain no RNA at all. However, it is possible that, as in the 

 case of phage infection in bacteria, the egg reacts to the penetration 

 of the spermatozoon by the production of new RNA or, at any 

 rate, by a change in RNA metabolism. In fact, Elson et ah (1954) 

 have observed a decrease in the RNA content following fertilization 

 of sea urchin eggs. But more sensitive methods involving fertiliza- 

 tion of eggs whose RNA has been previously labeled would be 

 required in order to study changes comparable to those which 

 occur in bacteria when they are infected by a phage. Such methods 

 are available but they have not yet been used for this type of study. 

 In any event, it would be of interest to see how far the analogy 

 between phage infection and fertilization could be pushed, for in 

 both cases the essential event is the injection of the genetic material 

 in the form of DNA into the recipient cell. 



Work done by Shaver (1953) on parthenogenesis in amphibian 

 eggs also suggests that RNA might play a role in fertilization. The 

 famous experiments of Bataillon (1910) have shown that mere prick- 



References p. 90/93 



