Evolution of the Genetic Code Review

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(More customer reviews)The genetic code, for example, the fact that 'AAA' in the mRNA codes for the addition of lysine amino acid to the growing protein chain, was formerly thought to be frozen since the same code was found in the initial lifeforms explored, and since logically a change in this fundamental code would simultaneously disrupt a large number of the cell's or organelle's proteins. However, continued research found exceptions to the genetic code. For example, in the mitochondria of echinoderms 'AAA' does not code for lysine but instead for the amino acid asparagine. This reference discusses the codon capture theory and how such evolution of the very fundamental genetic code could occur. In the echinoderm mitochondrial 'AAA' example, its ancestral tRNA-lysine had an anticodon that translated both 'AAA' and 'AAG' to lysine, which is correct according to the standard genetic code. Due to selective pressure of having a genome higher in content of G-C nucleotide pairs, the 'AAA' codon gradually was replaced by 'AAG' until the 'AAA' codon disappeared. In the standard genetic code asparagine is coded for by similar codons, 'AAU' and 'AAC'. Years later, as evolution continued, one day 'AAA' was 'recaptured' to be used as another code for the asparagine amino acid. This short, easy to read book shows that the genetic code is not an arbitrary theoretical construct, but is also subject to evolutionary pressures. Readers that are suspicious of phylogenetic representations of the evolution of life, ie, the splitting of eukaryotes, archaebacteria and eubacteria from the common ancestor billions of years ago, and the myriad of branchings since, may also want to review this reference to see how the DNA code in modern organisms can be used to infer branchings that occurred many millions of years ago.

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The genetic code was deciphered experimentally around 1966 and for a number of years scientists considered it to be "universal" for all forms of life. In 1981 researchers shocked the scientific community with the discovery that the code differed in mitochondria and certain other organisms, evidence that the genetic code was still evolving. This book discusses the distribution and origin of the non-universal codes and examines the possible mechanisms of code changes, making it essential reading for all those interested in evolutionary genetics.

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