The nucleosides, in turn, are subsequently broken down in the lumen of the digestive system by nucleosidases into nucleobases and ribose or deoxyribose.
DNA polymerases cannot distinguish between these and regular deoxyribonucleotides, but when incorporated a dideoxynucleotide cannot bond with the next base and the chain is terminated.
RNA is composed of purine and pyrimidine nucleotides, both of which are necessary for reliable information transfer, and thus Darwinian natural selection and evolution.
Nam et al.[5] demonstrated the direct condensation of nucleobases with ribose to give ribonucleosides in aqueous microdroplets, a key step leading to RNA formation.
Also, a plausible prebiotic process for synthesizing pyrimidine and purine ribonucleosides and ribonucleotides using wet-dry cycles was presented by Becker et al.[6]