Expanded genetic code

An expanded genetic code is an artificially modified genetic code in which one or more specific codons have been re-allocated to encode an amino acid that is not among the 22 common naturally-encoded proteinogenic amino acids.^[1]

The key prerequisites to expand the genetic code are:

the non-standard amino acid to encode,
an unused codon to adopt,
a tRNA that recognizes this codon, and
a tRNA synthetase that recognizes only that tRNA and only the non-standard amino acid.

Expanding the genetic code is an area of research of synthetic biology, an applied biological discipline whose goal is to engineer living systems for useful purposes. The genetic code expansion enriches the repertoire of useful tools available to science.

In May 2019, researchers, in a milestone effort, reported the creation of a new synthetic (possibly artificial) form of viable life, a variant of the bacteria Escherichia coli, by reducing the natural number of 64 codons in the bacterial genome to 61 codons (eliminating two out of the six codons coding for serine and one out of three stop codons) – of which 59 used to encode 20 amino acids.^[2]^[3]

^ Xie J, Schultz PG (December 2005). "Adding amino acids to the genetic repertoire". Current Opinion in Chemical Biology. 9 (6): 548–54. doi:10.1016/j.cbpa.2005.10.011. PMID 16260173.
^ Zimmer C (15 May 2019). "Scientists Created Bacteria With a Synthetic Genome. Is This Artificial Life? – In a milestone for synthetic biology, colonies of E. coli thrive with DNA constructed from scratch by humans, not nature". The New York Times. Retrieved 16 May 2019.
^ Fredens J, Wang K, de la Torre D, Funke LF, Robertson WE, Christova Y, et al. (May 2019). "Total synthesis of Escherichia coli with a recoded genome". Nature. 569 (7757): 514–518. Bibcode:2019Natur.569..514F. doi:10.1038/s41586-019-1192-5. PMC 7039709. PMID 31092918.

[1] Xie J, Schultz PG (December 2005). "Adding amino acids to the genetic repertoire". Current Opinion in Chemical Biology. 9 (6): 548–54. doi:10.1016/j.cbpa.2005.10.011. PMID 16260173.

[NYT-20190515-2] Zimmer C (15 May 2019). "Scientists Created Bacteria With a Synthetic Genome. Is This Artificial Life? – In a milestone for synthetic biology, colonies of E. coli thrive with DNA constructed from scratch by humans, not nature". The New York Times. Retrieved 16 May 2019.

[NAT-20190515-3] Fredens J, Wang K, de la Torre D, Funke LF, Robertson WE, Christova Y, et al. (May 2019). "Total synthesis of Escherichia coli with a recoded genome". Nature. 569 (7757): 514–518. Bibcode:2019Natur.569..514F. doi:10.1038/s41586-019-1192-5. PMC 7039709. PMID 31092918.

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