119 



Work on the incorporation of pyrimidines in template-directed reac- 

 tions is also important. Further study of template-directed reactions 

 should contribute to our understanding of the origins of nucleic 

 acid replication. 



The minimal living system must be self-duplicating and mutable, 

 and it must have, at least latently, the capacity for heterocatalysis for 

 bringing about chemical changes in the environment that support the 

 self-duplication function. In other words, a living thing must be 

 capable of rearranging the universe to produce more of itself; and the 

 "self must be capable of continual change. All of this implies infor- 

 mation storage, replication, retrieval, and utilization. Contemporary 

 life displays these properties in a combined protein/nucleic acid sys- 

 tem, so further work in this area is especially desirable. The major 

 unresolved problem is in the area of translation and genetic coding 

 which features the specific interactions of amino acids with nucleic 

 acids or short oligonucleotides, and formation of peptide bonds by 

 template mechanisms. Both are worth pursuing. The demonstration 

 of translation in an experimental model that combines both of the 

 above features is of the greatest importance. A wide variety of 

 experimental approaches is justified in the absence of a consensus on 

 precise mechanisms. 



The study of simple peptides or polypeptides as catalysts is 

 important in understanding how a genetic system, once started, 

 could have gained a selective advantage. The processes of replication 

 and translation might be more efficient or more selective when cata- 

 lyzed by protoenzymes rather than without them. Case models 

 which leave out catalysts will not tell the whole story. Since the 

 synthesis of molecules resembling proteins and nucleic acids requires 

 removal of water, it is not surprising that molecules which have been 

 studied as catalysts often lead to degradation rather than synthesis 

 when the reaction occurs in water solution. The study of condensed 

 phases, mineral surfaces, membranes, and other heterogeneous 

 systems may be more conducive to synthetic catalysis than the study 

 of the homogeneous aqueous phase. 



