An "age" has passed in the 40 years since we first observed recovery from radiation damage in irradiated bacteria. During the early 1930s, we had been discussing the possibility of rapid changes after radiation exposure with Farring- ton Daniels, Benjamin Duggar, John Curtis, and others at the University of Wisconsin. After working with living cells, we had concluded that organisms receiving massive insults must have a wide variety of repair mechanisms available for restoration of at least some of the essential properties of the cell. The problem was how to fmd and identify these recovery...

The excision-repair of ultraviolet-induced lesions in DNA involves a recogni- tion and incision step which is followed by excision of the damaged material, DNA repair resynthesis, and sealing of the fmal gap by polynucleotide ligase (e.g. Howard-Flanders, 1968). The initial incision step appears to require an endo- nuclease which is absent in the uvrA and uvrR mutants of E. eoli K12 (Braun et al., Part A of this book). The polAl strains are deficient in DNA polymerase I activity (de Lucia and Cairns, 1969) and are partially deficient in repairing single-strand breaks in DNA (incision breaks)...

Liane B. Russell Biology Division, Oak Ridge National Laboratory Oak Ridge, TN 37830 Composite individuals have always excited mankind's imagina- tion. Even the earliest recorded mythologies are full of fanciful examples of creatures such as centaurs, mermaids, androgynes, and winged horses. While real, naturally occurring, mosaics might not appear as spectacular to the popular mind, their study -- particu- larly in Drosophila and plants -- has made important contributions to genetics, starting relatively early in this century. In mammals, too, examples of mosaics resulting from early or late...

The plant world represents a vast renewable resource for production of food, chemicals and energy. The utilization of this resource is frequently limited by moisture, temperature or salt stress. The emphasis of this volume is on the molecular basis of osmoregulation, adaptation to salt and water stress and applica- tions for plant improvement. A unified concept of drought, salt, thermal and other forms of stress is proposed and discussed in the publication. The volume developed from a symposium entitled "Genetic Engi- neering of Osmoregulation: Impact on Plant Productivity for Food, Chemicals...

Not many years ago most discussion of mutation induction by physical and chemical agents concentrated on the initial lesions induced in the DNA with the implicit assumption that once the lesions were made they were converted almost automatically to mutations by relatively simple processes associated with DNA replication. The discovery of a variety of enzymatic processes that can repair these lesions, the great increase in our understanding of the molecular steps involved in repair, replication, and recombination, and the increasing availability of cells with genetic defects in these pro-...

The growing concern about where energy rich chemicals for the future will come from has stimulated a resurgence of interest in the potentialities of microbial fermentations to assist in meeting anti- cipated demands for fuels and chemicals. While much attention has been given recently to the early deployment of alcohol production plants and similar currently available technologies, the potential future developments have received much less attention. One of the intentions of the present symposium was to look ahead and try to perceive some of the prospects for future fermentation technology. In...

The normal course of most biologically catalyzed processes is tightly regulated at the genetic and physiological levels. The regulatory mechanisms are diverse, sometimes redundant, and it is becoming increasingly apparent that, at the genetic level, the range of mechanisms may be limited only by the permutations and combina- tions available. For each microbial cell, evolution appears to have resulted in maximized advantage to that cell, achieving regulatory balance. Genetic engineering encompasses our attempts to perturb the genetic regulation of a cell so that we may obtain desired other...

William C. Taylor Department of Genetics University of California Berkeley, California 94720 It is evident by now that there is a great deal of interest in exploiting the new technologies to genetically engineer new forms of plants. A purpose of this meeting is to assess the possibilities. The papers that follow are concerned with the analysis of single genes or small gene families. We will read about genes found within the nucleus, plastids, and bacteria which are responsible for agri- culturally important traits. Given that these genes can be isolated by recombinant DNA techniques, there...

Chromosomes. being well-defined structures that are easily vis- ible under the optical microscope. readily lend themselves to in- tense physical and biochemical study. The understanding of the structure and function of this most critical genetic material has progressed through a number of interesting stages. Often connected with the development of new techniques in staining and photography. using the standard microscope and the electron microscope. It is interesting to look back at the history of cytogenetics. I would like especially to emphasize the work of Karl Sax and many of his students....

The present workshop had its orlglns in discussions among Alexander Hollaender, Oddvar Nygaard, Donald Borg, Richard Setlow and Victor Bond on the need for a symposium that would deal with a broad spectrum of pressing subjects related to the physics, chemistry, and biological actions of ionizing radiations, and the theoretical and practical problems of risk assessment. It soon became apparent that the spectrum of subjects considered was too broad for the desired depth of coverage; in fact, it seemed un- likely that the conference participants would have the background knowledge to span the...