title: Evolving new genetic codes.
abstract: Although the genetic code is almost universal, natural variations exist that have caused evolutionary biologists to speculate about codon evolution. There are two predominant hypotheses that specify either a gradual (ambiguous intermediate) or stochastic (codon capture) change in the code. These hypotheses are similar to two biotechnology techniques that have been used to engineer the genetic code: a 'top down' approach, in which the whole organism is evolved for the ability to incorporate unnatural amino acids, and a 'bottom up' approach, in which aminoacyl-tRNA synthetases and their cognate tRNAs are engineered. The biotechnology experiments provide insights into natural codon evolution, and a combination of these approaches should enable the evolution of organisms that can incorporate unnatural amino acids throughout their proteomes.
authors.affiliation: Institute of Cellular and Molecular Biology, University of Texas at Austin, 1 University Station A4800, Austin, TX 78712, USA.
authors.forename: Jamie M
authors.initials: JM
authors.lastname: Bacher
authors.forename: Randall A
authors.initials: RA
authors.lastname: Hughes
authors.forename: J
authors.initials: J
authors.lastname: Tze-Fei Wong
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Ellington