genetic code Archives

tRNA evolved from RNA repeats and inverted repeats (stem–loop–stems) of known and conserved sequence. See the text for details. ACCA-Gly (line 6) was the primordial adapter molecule. Colors reflect internal homologies and are consistent throughout the figures. The tRNA precursor (line 11) was generated by the ligation of a 31 nt D loop minihelix (line 9, lacking 3′-ACCA) and two 31 nt anticodon (Ac) minihelices (line 10, lacking 3′-ACCA). Internally deleted bases are indicated in bold with strike-throughs. Bases in white bold are anticodon bases or sequence changes to support the tRNA fold. During pre-life, RNAs were formed with and without ligated 3′-ACCA. Underscored positions separate sequence elements and indicate how stem and loop sequences were selected. We posit that GCC may have been the primordial anticodon. GCC can utilize a GGC repeat (line 1) as a pre-mRNA. Secondary structures are indicated (parentheses stand for stems; * stands for loops). -- Genes

Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Genomics, Proteomics, Bioinformatics, Origin & Evolution of Life, Status Report

The Evolution Of The First Code

by Keith CowingJune 15, 2026

Background/Objectives: tRNAs, tRNAomes, aminoacyl-tRNA synthetases (AARSs), the first proteins, ribosomes and the genetic code coevolved. We utilize sequence data to reconstruct key steps in establishing the first code on Earth.

Evidence for ribozyme mass extinction. (A) Abundance distribution across all ten known small self-cleaving ribozyme families, showing the hammerhead's 91% dominance, a pattern characteristic of disaster taxa following mass extinction events. (B) Circular phylogeny of 80,548 unique hammerhead sequences colored by host taxonomic group. The star-like topology is consistent with post-bottleneck radiation, and the interspersion of distantly related host phyla around the tree reflects repeated independent colonization events rather than co-speciation, consistent with horizontal transfer of a single dominant survivor lineage. (C) Null distribution tests for Tajima's D (left) and Fu's Fs (right), each based on 10,000 coalescent replicates (n = 200, S = 40). Blue and orange histograms show the null distributions under neutral expectations; red dashed lines indicate the observed values (D = +2.28, upper-tail p = 0.013; Fs = −618.0, p < 0.0001). Observed D falls in the extreme upper tail (98.7% of null replicates below observed), indicating deep hierarchical structure; observed Fs falls far below any null replicate, indicating massive haplotype excess. The discordance between positive D and extremely negative Fs is diagnostic of ancient divergence preserved through a bottleneck followed by rapid within-lineage expansion. Full-sample values (n = 5,036) are D = +3.79, Fs = −690.8. -- biorxiv.org

Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Genomics, Proteomics, Bioinformatics, Origin & Evolution of Life, Status Report

A Ribozyme Mass Extinction At The RNA-cellular Boundary And Its Potential Imprint On The Genetic Code

by Keith CowingApril 13, 2026April 13, 2026

The transition from the RNA world to cellular life remains one of the least understood events in the history of biology.

Representation of the two main frameworks used to quantify molecular complexity: (a) graph-theoretic and b) information-theoretic approaches. Tryptophan is depicted as both a graph representation and a molecular structure, illustrating some of the key features captured by each framework. -- Genome Biology and Evolution via PubM

Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Genomics, Proteomics, Bioinformatics, Origin & Evolution of Life, Status Report

Molecular Complexity Constrained Early Amino Acid Recruitment into the Genetic Code

by Keith CowingMarch 5, 2026March 5, 2026

Previously proposed chronologies of amino acid incorporation into the genetic code rely on consensus rankings derived from prebiotic synthesis experiments, biosynthetic pathways, or genomic trends.

Journey of a noncanonical amino acid into a polypeptide. The cell takes up the ncAA from its environment or biosynthesizes it. The ncAA should not interfere with the host metabolism nor act as a toxin. To accumulate, it must not be degraded nor excreted by the cell. If its intracellular concentration reaches an adequate level, an aminoacyl-tRNA synthetase (AARS) activates it and charges it onto a tRNA. Discrimination against the ncAA by the editing function of some AARS prevents the downstream steps and should be avoided. An elongation factor delivers the ncAA-charged tRNA to the ribosome, where it participates in ribosomal translation. Peptide bonding stably incorporates the ncAA into the nascent polypeptide. The resulting alloprotein must be able to fold correctly and should not be degraded, e.g., by proteolytic enzymes. Chemical Reviews via PubMed

Astropharmacy / Biotechnology, Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Commercial & Private Sector, Genomics, Proteomics, Bioinformatics, Nanotechnology & SynBio, Press Release

Residue-Specific Incorporation of Noncanonical Amino Acids in Auxotrophic Hosts: Quo Vadis?

by Keith CowingSeptember 25, 2025September 25, 2025

The residue-specific incorporation of noncanonical amino acids in auxotrophic hosts allows the global exchange of a canonical amino acid with its noncanonical analog.

Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Genomics, Proteomics, Bioinformatics, Origin & Evolution of Life, Status Report

Order Of Amino Acid Recruitment Into The Genetic Code Resolved By The Last Universal Common Ancestor’s Protein Domains

by Keith CowingDecember 27, 2024

The current “consensus” order in which amino acids were added to the genetic code is based on potentially biased criteria, such as the absence of sulfur-containing amino acids from the […]

Biochemistry & Organic Chemistry, Biophysics, Genomics, Proteomics, Bioinformatics, Origin & Evolution of Life, Status Report

Structural Enzymology, Phylogenetics, Differentiation, and Symbolic Reflexivity at the Dawn of Biology

by Keith CowingDecember 23, 2024December 23, 2024

The reflexive translation of symbols in one chemical language to another defined genetics. Yet, the co-linearity of codons and amino acids is so commonplace an idea that few even ask […]

The evolutionary history of a protein domain may date back further in time than that of the whole-gene ortholog that it is part of. Multidomain genes 3 and 4 originated around the same time. However, they are made up of two protein domains (blue and orange boxes) that emerged and diverged at different points in time—domain 1 is older than domain 2. -- PNAS

Biochemistry & Organic Chemistry, Biosignatures & Paleobiology, Genomics, Proteomics, Bioinformatics, Habitable Zones, Origin & Evolution of Life, Press Release

Study Sheds Light On The Origin Of The Genetic Code

by Keith CowingDecember 13, 2024

Despite awe-inspiring diversity, nearly every lifeform – from bacteria to blue whales – shares the same genetic code. How and when this code came about has been the subject of […]

LUCA clans inform the origins of the current genetic code, while pre-LUCA clans reflect a still older system. Colored sequences emerged at different stages during the construction of the current genetic code. Grey sequences emerged under some more ancient, unknown, nowextinct coding mechanism(s). By current code, we include not just the canonical code, but also its direct ancestors. -- biorxiv.org

Biochemistry & Organic Chemistry, Biophysics, Biosignatures & Paleobiology, Genomics, Proteomics, Bioinformatics, Origin & Evolution of Life, Status Report

Identifying The Last Universal Common Ancestor’s Protein Domains Resolves The Order In Which The Amino Acids Were Recruited Into The Genetic Code

by Keith CowingApril 23, 2024April 23, 2024

We identified protein domains that emerged early in the history of life. Protein domains whose ancestors date back to a single homolog in the Last Universal Common Ancestor (LUCA) remain […]

a, Schematic illustrating the strategy of reversing the HPRT1 sequence to produce the HPRT1R sequence. b, The human HPRT1 locus was cloned into a assemblon vector and flanked by lox recombination sites for Big-IN integration. HPRT1R was assembled de novo from 28 synthetic segments, shown below the locus. Vector components include centromere (CEN)–autonomously replicating sequence (ARS) and LEU2 for propagation and selection in S. cerevisiae, bacterial artificial chromosome (BAC) oriS and oriV (low copy and inducible high copy origins, respectively) and the kanamycin resistance gene (Kanr) for propagation and selection in Escherichia coli, and eGFP–T2A–BSD for transient selection in mammalian cells. Chr., chromosome. c, Genomic contexts for interrogating synthetic locus activity. Episomal (Epi) and genomically integrated (chromosome XI) in S. cerevisiae, and genomically integrated (chromosome X and chromosome 3) in M. musculus. The chromosome 3 integration is monoallelic on the BL6 locus, leaving Sox2 intact on the CAST locus. d,e, DNA sequencing coverage plots from next-generation sequencing verification of assembled and integrated synthetic loci. Yeast samples were whole-genome sequenced and mouse ES cell samples were characterized by Capture-seq. Sc Epi, episomal in S. cerevisiae; Sc chr. XI, integrated on S. cerevisiae chromosome XI; Mm chr. X, integrated on M. musculus chromosome X; Mm chr. 3, integrated on M. musculus chromosome 3. (1) and (2) indicate two independent mouse ES cell clones. GC content shown as a line plot and colour-scaled. For HPRT1 Mm chr. X (1), dotted lines on the right show 2x coverage depth for most of the synthetic locus and 1x coverage depth at the edges. The relative position of the reversed HPRT1 coding sequence is indicated above the BAC in b and below the coverage plots in e.

Origin & Evolution of Life, Press Release

Synthetic DNA Sheds Light On Mysterious Difference Between Living Cells At Different Points In Evolution

by Keith CowingMarch 7, 2024March 7, 2024

“Random DNA” is naturally active in the one-celled fungi yeast, while such DNA is turned off as its natural state in mammalian cells, despite their having a common ancestor a […]

Volume-adjusted proximity probability distributions for a select different combinations of amino acids and nucleotides. Proximity is the closest atom of the nucleotide to the closest atom of the closest of 10 amino acids in the 40 Å periodic box. Proportion of simulation time is adjusted for the volume of the amino acid and nucleotide, so that different systems are comparable. Most interactions demonstrate multiple binding modes, at ~1.9 Å, 2.5 Å, and 4 Å. An additional peak at around 5.5 Å is also visible, which is interpreted as the average distance of the closest amino acid when not bound. The vertical red line indicates the 5 Å threshold for binding. (A) proline; (B) arginine; (C) aspartate; (D) phenylalanine; (E) glycine. -- Life

Biophysics, Genomics, Proteomics, Bioinformatics, Origin & Evolution of Life, Status Report

Biophysical Interactions Underpin the Emergence of Information in the Genetic Code

by Keith CowingMay 30, 2023May 26, 2023

The genetic code conceals a ‘code within the codons’, which hints at biophysical interactions between amino acids and their cognate nucleotides. Yet, research over decades has failed to corroborate systematic […]

genetic code

The Evolution Of The First Code

A Ribozyme Mass Extinction At The RNA-cellular Boundary And Its Potential Imprint On The Genetic Code

Molecular Complexity Constrained Early Amino Acid Recruitment into the Genetic Code

Residue-Specific Incorporation of Noncanonical Amino Acids in Auxotrophic Hosts: Quo Vadis?

Order Of Amino Acid Recruitment Into The Genetic Code Resolved By The Last Universal Common Ancestor’s Protein Domains

Structural Enzymology, Phylogenetics, Differentiation, and Symbolic Reflexivity at the Dawn of Biology

Study Sheds Light On The Origin Of The Genetic Code

Identifying The Last Universal Common Ancestor’s Protein Domains Resolves The Order In Which The Amino Acids Were Recruited Into The Genetic Code

Synthetic DNA Sheds Light On Mysterious Difference Between Living Cells At Different Points In Evolution

Biophysical Interactions Underpin the Emergence of Information in the Genetic Code

Underwater Oxygen Loss Threatens Earth’s Stability, Researchers Warn

Fire And Ice: Were Yellowstone’s Past Volcanic Eruptions And Glaciations Related?

Substrate-Agnostic 3x: Biosignatures, Technosignatures, Ecologies

Planet-moon Ejections In Close Stellar Encounters

First Study Hints Solar Storms May Alter The Weather During Martian Dust Storms