Heredity (1976),36 (3), 423-432

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STADLER GENETIC SYMPOSIA, Vol. 7 (1975). Edited by G. P. Redei. Agricultural Experimental Station, University of Missouri, Columbia, Missouri. Pp. 168. $4.50 +500 postage. Thelatest addition to this now well-established series contains the usual good measure of solid and timely articles. This year molecular genetics pre- dominates. Two papers deal with in vitro genetics. Robert Helling, who with Boyer and others, has been among the pioneers in the construction of artificial recombinant DNA molecules, contributes a most useful review on the transfer of eukaryotic genes to prokaryotic cells and their activity (so far rather limited) when they get there. Noboru Sueoka, writing on "Genetictrans- formation as a tool for studying DNA replication and recombination ",isa little disappointing. The applications to replication, though excellently described, are not very new, while what is said about recombination is hardly more than a promise of future work. Two other papers relate to molecules in evolution. That most fashionable subject, enzyme poly- morphims, is given a new twist by George Johnson's contribution. This paper is likely to be much referred to for its advocacy and description of a more refined and critical method for discriminating between what appear at first sight to be electrophoretically identical allele products. Johnson's general message is that there are likely to be many more alleles in populations than electrophoresis under a single set of conditions reveals, and one cannot doubt that he is right. Allan Wilson's paper deserves special mention for its bringing together of information on protein sequence on the one hand and karyotypes on the other in order to speculate on long term evolution. He concludes that sequence divergence proceeds at a rather similar rate in diverse groups of organisms, in contrast to the greatly accelerated morpho- logical diversification which has occurred in some groups (notably mammals) as compared with others. He points out that morphological divergence correlates with chromosomal restructuring and also with the development of crossing barriers between populations. He suggests that relatively rapid morphological evolution is a manifestation of changes in gene regulation, following chromosome rearrangement, rather than of changes in the struc- tural gene sequences—an interesting and stimulating idea. As befits a Stadler Symposium, several papers deal with plants, though the one by Richard Flavell and Derek Smith is of broader relevance. They explain in detail the kinds of experiment from which one can derive at least a rough picture of the sizes and arrangement of unique and reiterated sequences in the whole genome. Now that DNA reannealing analysis is so popular, it is useful to have this well-illustrated account of the underlying rationale. Of the other papers on plants, that by Donald Miles, on the genetic analysis of photosynthesis, is a good progress report on a complex field, while Oluf Gamborg's contribution of cell hybridisation in higher plants convinces at least this reviewer that, contrary to what one might think from some of the more optimistic stories in the press, there is still some way to go before 423 424 REVIEWS manipulations with somatic cells, fascinating though they are, add very significantly to what can be achieved by more conventional methods of plant breeding. The first and last contributions to the Symposium are rather more light. weight. Dean Miller's concluding paper on "Natural selection and adaptive resemblances" is a pleasant and easy introduction to the subject. Erwin Chargaff's opening essay—" A few remarks on the impact of biochemistry of genetics "—is odd. It promises something of interest but what we get is more of the author's usual bitter sarcasm at the expense of molecular biology. One wonders why he came. J. R. S. FINCHAM Department of Genetics, University of Leeds

THECONTROL OF GENE EXPRESSION IN ANIMAL DEVELOPMENT. J. B. Gurdon. Clarendon Press: Oxford University Press. Pp. 160+29 figures. £350 (hard cover), £1 25 (paperback). "Howis gene expression controlled, and what determines the distribution of materials in and among cells? These are the two most important questions in animal development." Few biologists will disagree with these opening statements to John Gurdon's recent book. This book originated from the Dunham Lectures delivered in 1971 to the Harvard Medical School and is mainly concerned with the first of these two questions. The book can be highly recommended to all biologists with an interest in developmental biology. Not only does it give an authoritative account of Gurdon's own work over the last 15 years but it does so in a very readable and attractive way. The three main chapters of the book cover, in turn, the three main levels at which the control of gene expression may be exercised: differential DNA replication or gene mutation, differential translation of mRNAs and differen- tial gene transcription. It is important to note what this book is not, it is not a textbook of modern developmental biology nor even a comprehensive review of current research in this rapidly expanding field. It is a very stimulating discussion of the contribution of various techniques, especially those involving nuclear transplantation and mRNA injection into oocytes, to the experimental analysis of certain aspects of development. The emphasis is on experimental rigour though never to the point of pedantry. The conclusion drawn in the first chapter of this book, "that the nuclei of different kinds of cells in an individual appear to be genetically identical" is one which is generally accepted today. True, there are cases known which contradict it; the elimination of chromosomes (or chromatin) from somatic cell nuclei seen in organisms as diverse as the ciliate protozoa and various flies is well known, if not well understood. But these are exceptions and cannot be used to invalidate the general rule. Much of this Chapter con- siders the conclusions drawn from the amphibian nuclear transplant experiments, experiments designed to test the potential of nuclei from differentiated, or developing cells, in a most direct way. Interestingly the results of these experiments have lead to both support for and opposition to the idea that, in general, cellular differentiation is neither the result of, nor results in, stable nuclear changes. Gurdon reviews this question in detail