In Search of RNA Ancestors

Abstract

The recent discoveries of catalytically active RNA species have reinforced the view that a key step in the emergence of life on earth may have been the development of self-replicating RNA molecules. Although much progress has been made in recent years toward the development of an experimental model of RNA replication, there remain many problems that have yet to be overcome (Joyce et al. 1984a; Joyce and Orgel 1986). Perhaps the most serious difficulty is that of understanding the prebiotic synthesis of the nucleosides and of the specifically phosphorylated and activated derivatives required for template-directed reactions. The major obstacle in the formation of the nucleosides is not the synthesis of purines and pyrimidines, for which quite reasonable pathways are available (at least for adenine and uracil), rather, it is the question of the source of ribose and deoxyribose that has remained troublesome over the years. Although the “formose” reaction is...