Recent evidence for evolution of the genetic code

  title={Recent evidence for evolution of the genetic code},
  author={S. Osawa and Thomas Hughes Jukes and K Watanabe and Akira Muto},
  journal={Microbiological Reviews},
  pages={229 - 264}
The genetic code, formerly thought to be frozen, is now known to be in a state of evolution. This was first shown in 1979 by Barrell et al. (G. Barrell, A. T. Bankier, and J. Drouin, Nature [London] 282:189-194, 1979), who found that the universal codons AUA (isoleucine) and UGA (stop) coded for methionine and tryptophan, respectively, in human mitochondria. Subsequent studies have shown that UGA codes for tryptophan in Mycoplasma spp. and in all nonplant mitochondria that have been examined… 

Evolution of the genetic code in yeasts

A unique genetic code change involving the decoding of the leucine CUG codon as serine was discovered in the cytoplasm of Candida and Debaryomyces species, indicating that the genetic code of yeasts may be under specific evolutionary pressures whose molecular nature is not yet fully understood.

A non‐canonical genetic code in an early diverging eukaryotic lineage.

Confirmation of a variant code in which TAR codes for glutamine is found by identifying genes encoding glutamine‐tRNAs with CUA and UUA anticodons in H.inflata, an early‐diverging eukaryotic lineage.

Parallel Evolution of the Genetic Code in Arthropod Mitochondrial Genomes

This work has investigated the evolution of the genetic code in the arthropods and found several events of parallel evolution in which the AGG codon was reassigned between serine and lysine, and correlated evolution between theArthropod genetic codes and the tRNA-Lys/-Ser, which show specific point mutations at the anticodons.

Directionally Evolving Genetic Code: The UGA Codon from Stop to Tryptophan in Mitochondria

It is proposed that the ancestral mitochondrion was bearing the universal genetic code and subsequently reassigned the codon to Trp independently, at least in the lineage of ciliates, kinetoplastids, rhodophytes, prymnesiophyte orders, and fungi.

UAR Codons for Glutamine

The proposal for UAR-bearing codons for glutamine was (and is) as follows:.

1979 Genetic Code

Alternative genetic code for amino acids and transfer RNA revisited

Surprisingly, although higher eukaryotes, such as the nematode (worm), utilize the standard genetic code, newly identified nematodes-specific tRNAs (nev-tRNAs) translate nucleotides in a manner that transgresses the code.

Natural expansion of the genetic code.

The existence of phosphoseryl-tRNA (in the form of tRNACys and tRNASec) may presage the discovery of other cotranslationally inserted modified amino acids.

A novel nuclear genetic code alteration in yeasts and the evolution of codon reassignment in eukaryotes

It is shown that in Pachysolen CUG codons are translated as alanine and not as the universal leucine, which applies to all nuclear genetic code alterations and provides several testable predictions.



Novel features in the genetic code and codon reading patterns in Neurospora crassa mitochondria based on sequences of six mitochondrial tRNAs.

An expanded codon-reading ability of certain mitochondrial tRNAs will explain how the mitochondrial protein-synthesizing system operates with a much lower number of tRNA species than do systems present in prokaryotes or in eukaryotic cytoplasm.

Apparent lack of discrimination in the reading of certain codons in Mycoplasma mycoides.

We report a cluster of four tRNA genes from Mycoplasma mycoides as well as the sequence of the alanine, proline, and valine tRNAs and the serine tRNA reading the UCN codons (where N stands for G, A,

The signal for the termination of protein synthesis in procaryotes.

It is suggested that for the efficient termination of protein synthesis in E. coli, the 'stop signal' may be a tetranucleotide, rather than simply a tri-nucleotide codon, and that polypeptide chain release factor-2 recognises this extended signal.

Directional mutation pressure and transfer RNA in choice of the third nucleotide of synonymous two-codon sets.

  • S. OsawaT. Ohama K. Umesono
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 1988
The results demonstrate that tRNA levels act additively to A.T and G.C/A.C pressure in affecting contents of A (pairing with *UNN anticodons, in which *U indicates a 2-thiouridine derivative) and C ( Pairing with GNN anticodONS) or G (paired with CNN anticodon), respectively, in third nucleotide positions of codons.

The codon CUG is read as serine in an asporogenic yeast Candida cylindracea

Another example of divergence from the universal code is reported in a non-spore-forming yeast Candida cylindracea, in which the uni-versal codon for leucine, CUG, is used to code for serine.

Codon recognition rules in yeast mitochondria.

The mitochondrial genome of Saccharomyces cerevisiae codes for 24 tRNAs and it is of interest that the CGN codons have not been found in the mitochondrial genes sequenced to date.

Differential use of termination codons in ciliated protozoa.

  • D. S. HarperC. Jahn
  • Biology
    Proceedings of the National Academy of Sciences of the United States of America
  • 1989
This work has sequenced the linear DNA molecules that carry an actin gene and a beta-tubulin gene from the ciliate Euplotes crassus and shows that TAA uses TAA as a termination codon, indicating that the timing of genetic code changes in the ciliates must be reconsidered.