Plant cells contain various types of plastid, the best known among which is the chloroplast. Apart from their predominant interest for the work on photo synthesis, however, chloroplasts have attracted considerable attention for other reasons. This pertains to extranuclear inheritance of cell organelles and, particularly important for this series, to the participation of chloroplasts as discrete and partly autonomous cell constituents in the developmental biochemistry of plants. This volume is composed of articles by investigators who are actively involved in work on various aspects of...

The form and function of every living organism on the earth depends on the complex regulation of gene expression. This is carried out by controlling and interdigitating spatial and temporal patterns of gene activity during the life time of eukaryotic organisms. This is most dramatically apparent during early stages of development, when new types of cells and organs are being formed, often during very short time spans. To achieve this, it is vital that developmentally important genes can be kept in inactive or active states which are stably inherited in the soma. Indeed, it is now wellknown...

L. Nover and L. Hightower Though the roots of experimental stress biology at the cellular and organismic level can be traced back to the middle of the last century (Nover 1989), a decisive breakthrough came only in 1962 with the report on stress-induced changes of gene activity in Drosophila (Ritossa 1962) and the subsequent identification of the newly synthesized heat stress proteins (Tissieres et al. 1974) and mRNAs, respectively (McKenzie et al1975; McKenzie and Meselson 1977). The selectivity of induction and the high rate of accumulation of Hsps facilitated the cloning and sequencing of...

The control of plant gene expression at the transcriptional level is the main subject of this volume. Genetics, molecular biology and gene technology have dramatically improved our knowledge of this event. The functional analysis of promoters and transcription factors provides more and more insights into the molecular anatomy of initiation complexes assembled from RNA polymerase and the multiplicity of helper and control proteins. Formation of specific DNA-protein complexes - activating or repressing transcription - is the crux of developmental or environmental control of gene expression. The...

Till recently, mutations in genes were described in textbooks as deletions or point mutations. These mutations can be inherited from a parent or they are de novo alterations. The discovery in 1991 that human disease can be caused by large-scale ex pansion of highly unstable trinucleotide repeats has elucidated a new mutation mechanism, heritable unstable DNA. In the subsequent years more then 10 such disease genes have been identified. All dynamic mutations have been iden tified in neurological disorders. There are ten possible trinucleotide repeats at the DNA level, but only 3 have been...

The molecular genetics of aging or life-span determination is an expanding field. One reason is because many people would consider it desirable if hu man life span could be extended. Indeed, it is difficult not to be fascinated by tales of the life and death of people who have succeeded in living a very long life. Because of this, we have placed at the head of this book the chapter by Perls et al. on Centenerians and the Genetics of Longevity. Perls and his coauthors convincingly argue that, while the average life expectancy might be mostly determined by environmental factors because the...

Earlier titles in this series have directed attention to selected questions of current theoretical or practical interest in developmental biology, without special emphasis upon individual biological systems. Tho choose giant polytene chromosomes as the common denominator of a new volume may at first sight seem to set rather arbitrary restrictions upon a coherent discussion of the basic problem of cellular differentiation. However, the reader will find out for hirnself that, on the contrary, such a limitation, though dicta ted by the material, focuses the analysis upon one essential point: the...

It is instructive to compare the response of biologists to the two themes that comprise the title of this volume. The concept of the cell cycle-in contra distinction to cell division-is a relatively recent one. Nevertheless biologists of all persuasions appreciate and readily agree on the central problems in this area. Issues ranging from mechanisms that initiate and integrate the synthesis of chro mosomal proteins and DNA during S-phase of mitosis to the manner in which assembly of microtubules and their interactions lead to the segregation of metaphase chromosomes are readily followed by...

The relationship of cell lineage and differentiation is one of the most intriguing problems in developmental biology. In most higher organisms, the analysis of the cell lineage has to rely on indirect methods. Only in the most suitable systems, like the nematodes, can the pattern of cell division be determined by direct observation under the microscope. In cases where this is not possible, the fate of the cells has to be examined by using cell markers. Most suitable for this purpose are genetic markers, provided that they do not interfere with the developmental pathway to be studied. However,...

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