Theoretical minimal RNA rings attempt to mimick life's primitive RNAs. At most 25 22-nucleotide-long RNA rings code once for each biotic amino acid, a start and a stop codon and form a stem-loop hairpin, resembling consensus tRNAs. We calculated, for each RNA ring's 22 potential splicing positions, similarities of predicted secondary structures with tRNA vs. rRNA secondary structures. Assuming rRNAs partly derived from tRNA accretions, we predict positive associations between relative secondary structure similarities with rRNAs over tRNAs and genetic code integration orders of RNA ring anticodon cognate amino acids. Analyses consider for each secondary structure all nucleotide triplets as potential anticodon. Anticodons for ancient, chemically inert cognate amino acids are most frequent in the 25 RNA rings. For RNA rings with primordial cognate amino acids according to tRNA-homology-derived anticodons, tRNA-homology and coding sequences coincide, these are separate for predicted cognate amino acids that presumably integrated late the genetic code. RNA ring secondary structure similarity with rRNA over tRNA secondary structures associates best with genetic code integration orders of anticodon cognate amino acids when assuming split anticodons (one and two nucleotides at the spliced RNA ring 5' and 3' extremities, respectively), and at predicted anticodon location in the spliced RNA ring's midst. Results confirm RNA ring homologies with tRNAs and CDs, ancestral status of tRNA half genes split at anticodons, the tRNA-rRNA axis of RNA evolution, and that single theoretical minimal RNA rings potentially produce near-complete proto-tRNA sets. Hence genetic code pre-existence determines 25 short circular gene- and tRNA-like RNAs. Accounting for each potential splicing position, each RNA ring potentially translates most amino acids, realistically mimicks evolution of the tRNA-rRNA translation machinery. These RNA rings 'of creation' remind the uroboros' (snake biting its tail) symbolism for creative regeneration.

中文翻译：

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Uroboros 生命起源理论：22 核苷酸理论最小 RNA 环反映了遗传密码和 tRNA-rRNA 翻译机器的进化

理论上的最小 RNA 环试图模仿生命的原始 RNA。最多 25 个 22 核苷酸长的 RNA 环为每个生物氨基酸、一个起始密码子和一个终止密码子编码一次，并形成一个茎环发夹，类似于共有 tRNA。我们计算了每个 RNA 环的 22 个潜在剪接位置，预测的二级结构与 tRNA 与 rRNA 二级结构的相似性。假设 rRNA 部分源自 tRNA 增生，我们预测与 rRNA 在 tRNA 上的相对二级结构相似性与 RNA 环反密码子同源氨基酸的遗传密码整合顺序之间存在正相关。分析将每个二级结构的所有核苷酸三联体视为潜在的反密码子。古老的化学惰性同源氨基酸的反密码子在 25 个 RNA 环中最为常见。对于根据 tRNA 同源性衍生的反密码子、tRNA 同源性和编码序列一致的具有原始同源氨基酸的 RNA 环，对于可能在遗传密码晚期整合的预测同源氨基酸，这些是分开的。当假设反密码子分裂（剪接的 RNA 环 5' 和 3' 末端分别有一个和两个核苷酸）时，RNA 环二级结构与 tRNA 二级结构上的 rRNA 相似性与反密码子同源氨基酸的遗传密码整合顺序最相关，并且在预测时剪接的 RNA 环中间的反密码子位置。结果证实了 RNA 环与 tRNA 和 CD 的同源性、tRNA 半基因在反密码子处分裂的祖先状态、RNA 进化的 tRNA-rRNA 轴，以及单个理论上的最小 RNA 环可能产生近乎完整的原 tRNA 集。因此遗传密码预先存在决定了 25 个短的环状基因和 tRNA 样 RNA。考虑到每个潜在的剪接位置，每个 RNA 环都可能翻译大多数氨基酸，实际上模拟了 tRNA-rRNA 翻译机制的进化。这些“创造”的 RNA 环提醒了 uroboros（蛇咬尾巴）对创造性再生的象征意义。