Lazcano A, Guerrero R, Margulis L, Oró J
Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, IPN, México, Distrito Federal.
J Mol Evol. 1988;27(4):283-90. doi: 10.1007/BF02101189.
The evolution of genetic material can be divided into at least three major phases: first, genomes of "nucleic acid-like" molecules; secondly, genomes of RNA; and finally, double-stranded DNA genomes such as those present in all contemporary cells. Using properties of nucleic acid molecules, we attempt to explain the evolutionary transition from RNA alone as a cellular informational macromolecule prior to the evolution of cell systems based on double-stranded DNA. The idea that ribonucleic acid-based cellular genomes preceded DNA is based on the following: (1) protein synthesis can occur in the absence of DNA but not of RNA; (2) RNA molecules have some catalytic properties; (3) the ubiquity of purine and pyridine nucleotide coenzymes as well as other similar ribonucleotide cofactors in metabolic pathways; and (4) the fact that the biosynthesis of deoxyribonucleotides always proceeds via the enzymatic reduction of ribonucleotides. The "RNA prior to DNA" hypothesis can be further developed by understanding the selective pressures that led to the biosynthesis of deoxyribose, thymine, and proofreading DNA polymerases. Taken together these observations suggest to us that DNA was selected as an informational molecule in cells to stabilize earlier RNA-protein replicating systems.(ABSTRACT TRUNCATED AT 250 WORDS)
第一，“类核酸”分子的基因组；第二，RNA基因组；最后是双链DNA基因组，如所有现代细胞中存在的基因组。利用核酸分子的特性，我们试图解释在基于双链DNA的细胞系统进化之前，仅由RNA作为细胞信息大分子的进化转变。基于RNA的细胞基因组先于DNA的观点基于以下几点：（1）蛋白质合成可以在没有DNA但不能没有RNA的情况下发生；（2）RNA分子具有一些催化特性；（3）嘌呤和吡啶核苷酸辅酶以及其他类似的核糖核苷酸辅因子在代谢途径中普遍存在；（4）脱氧核糖核苷酸的生物合成总是通过核糖核苷酸的酶促还原进行。通过理解导致脱氧核糖、胸腺嘧啶和校对DNA聚合酶生物合成的选择压力，可以进一步发展“DNA之前的RNA”假说。综合这些观察结果，我们认为DNA在细胞中被选为信息分子，以稳定早期的RNA-蛋白质复制系统。（摘要截断于250字）
