Molecular fossils of an ancestral code revealed by large-scale analysis of tRNAs.

Cognate anticodon-like triplets are significantly enriched in acceptor stems of modern tRNAs for certain amino acids, supporting remnants of an ancestral coding system.

• Why it matters: Understanding how the genetic code evolved is crucial for insights into the origin of life and molecular evolution, yet direct evidence of early coding relationships remains limited.
• What they did: Analyzing 77,335 tRNA sequences with a structure-aware statistical framework, the study identified amino acid-specific enrichment of anticodon-like triplets in acceptor stems, especially for those supporting minihelix aminoacylation.
• The result: These signals persist after null models and cluster against amino acid incorporation chronologies, suggesting molecular fossils of an ancestral operational code that inform the evolution of codon-amino acid relationships.