MOLECULAR PHYLOGENETICS AND EVOLUTION

Vol. 6, No. 2, October, p. 320, 1996ARTICLE NO. 0082

BOOK REVIEW

Evolution of the Genetic Code. By Syozo Osawa. is packed with hare-brained wheezes about where thecode came from, none of which can be disproven withOxford University Press, New York, 1995. 205 pp.,

$105.00. current technology. Osawa reviews many of the moresensible ones, particularly his own widely accepted ‘‘co-don capture’’ theory of how a codon can switch meaningA whole book about 64 codons? Syozo Osawa’s mono-

graph, written in 1993–1994 to mark the occasion of his if it first becomes ‘‘unassigned’’ through disuse, typi-cally by being at the receiving end of strong directionalretirement from Nagoya University, runs about three

pages per codon. Much of the book is occupied by factual mutation pressure on G1C content. Perhaps the moredifficult questions are those about the origins of thebut rather dull tables and descriptions of the vagaries

of codon:anticodon pairing in various organisms and code itself: Why use this particular set of 20 aminoacids? Does the use of similar codons for chemicallycontexts, abundantly making the point that, contrary

to what was thought between 1966 and 1979, the ge- similar amino acids betray a more ancient, simplercode? What is the significance of the two families ofnetic code is neither universal nor frozen.

It is only in the final few chapters that the question aminoacyl-tRNA synthetases?There are some gems in this book, including Eigen’sof evolution per se is addressed. This question takes

two forms: First, how can the genetic code change (as reassuring calculation that the genetic code is no olderthan Planet Earth. Osawa informs us that God uses theit does, for example, in mitochondria)? And second,

where did the code come from in the first place? The universal genetic code. But the net impression fromthis book is that we can do little beyond observing andtrouble with the genetic code is that we are presented

with a fait accompli: a fully fledged code that is virtu- speculating. Can we ever catch an organism ‘‘in the act’’of changing its genetic code? Perhaps we will find an-ally universal across all organisms and therefore was

in place more than three billion years ago. The code is swers in the era of genome sequences, such as those ofMycoplasma genitalium (which translates CGG as Arg)so fundamental to the life of the cell that we can per-

form only the most rudimentary experiments on it; and Mycoplasma capricolum (where CGG is unas-signed and the corresponding tRNA does not exist).most insights have been gleaned from the occasional

discovery of organisms whose codes deviate from theuniversal (usually in pretty minor ways), or genes that KEN WOLFE

contain nonstandard codons such as UGA for selenocys- Department of Geneticsteine. University of Dublin

The code’s elegance and simplicity beg speculation Trinity Collegeabout its origin and subsequent evolution. And its lack Dublin 2, Irelandof experimental tractability means that the literature

3201055-7903/96 $18.00Copyright 1996 by Academic Press, Inc.All rights of reproduction in any form reserved.