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[
1981]
A neuron can be characterized by its morphology, transmitter (s?), receptor(s) and the nature of its synaptic contacts (chemical or electrical; excitatory or inhibitory; number and distribution of synapses; identity of the cells to which it is presynaptic or postsynaptic). It is clear that according to such criteria nervous sytems consist of neurons of many distinct types. The origin of neuronal diversity is unknown. Both how such diversity is generated during development and how the relevant developmental programme is encoded in the genome remain to
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[
Methods Cell Biol,
1995]
The purpose of this chapter is to provide a practical guide to immunofluorescence microscopy of Caenorhabditis elegans. In this method, fixed tissue is stained with a fluorescently labeled antibody and visualized with the light microscope. The antibody ensures that staining is limited to the location of the antigen, and the microscope provides a magnified image of the fluorescent area. Immunofluorescence microscopy is an especially powerful tool for studies of C. elegans. The identity of each antibody-stained cell can be determined by reference to detailed knowledge of C. elegans anatomy. Because the developmental cell lineage is known, it is also possible to define the timing of antigen expression with great precision. Because of the transparency and small size of the animal, immunofluorescence staining can be clearly observed in whole mounts and does not require
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[
WormBook,
2005]
The mitochondrial genome is vital for Caenorhabditis elegans metabolism, physiology, and development. The C. elegans mitochondrial DNA is typical of animal mitochondrial genomes in its size and gene content. It is 13,794 nucleotides in length and encodes 36 genes: 2 ribosomal RNAs, 22 transfer RNAs, and 12 protein subunits of the mitochondrial respiratory chain. Although it represents only a small number of genes, an elaborate cellular machinery comprised of over 200 nuclear genes is needed to replicate, transcribe, and maintain the mitochondrial chromosome and to assemble the translation machinery needed to express this dozen proteins. Mitochondrial genetics is peculiar and complex because mitochondrial DNA is maternally inherited and can be present at tens to tens of thousands of copies per cell. The mitochondrial genome content of the developing nematode is developmentally regulated; it increases about 30-fold between the L1 and the adult stages and blocking the increase leads to larval arrest. Energy metabolism is also intimately linked to aging and lifespan determination. The nematode model system offers numerous advantages for understanding the full importance and scope of the mitochondrial genome in animal life.
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[
Methods Cell Biol,
1995]
Caenorhabditis elegans is in all likelihood the first metazoan animal whose entire genome will be determined. In addition, a very detailed description of the animal's morphology, development, and physiology is available (see elsewhere in this book, and Wood, 1988). Thus, the complete phenotype and genotype of an animal will be known. What is not known is how genotype determines phenotype; to study this, one needs to establish connections between genome sequence and phenotypes. Much has been done by classic or forward genetics: mutagenesis experiments have identified loci involved in a specific trait. Many of these loci have already been defined at the molecular level, and the genome sequence will certainly aid in the identification of many more. The opposite approach, reverse genetics, becomes naturally more important when more of the genome sequence is determined: Given the sequence of a gene of which nothing else is know, how can the function of that gene be determined? Reverse genetics is more than targeted inactivation. One can study a gene's function by several approaches...|
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[
Methods Cell Biol,
1995]
The nematode Caenorhabditis elegans is a small, rapidly growing organism that can easily be raised in the laboratory on the bacterium Escherichia coli. Because C. elegans is a self-fertilizing hermaphrodite, it is possible to readily grow large quantities of the organism in swirling liquid cultures and also possible to propagate severely incapacitated mutants. The rapidity of growth and the ability to self-fertilize necessitate special measures to establish a synchronous culture.
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Meiosis is the process by which eukaryotes reduce their chromosome content by half. During meiosis, the chromosomes undergo two divisions, the first of which involves the organized synapsis of homologous chromosomes. During this division, synapsis predisposes the chromosomes to recombination and proper disjunction. We review here aspects of meiotic recombination under study using the self-fertilizing hermaphroditic nematode Caenorhabditis elegans. Six linkage groups wre identified by Brenner that correlated with the six chromosomes observed by Nigon. Although the behavior of the chromosomes is reported to be holokinetic, we have not needed to invoke any unusual mechanisms to explain their behavior with regard to meiotic recombination. On the contrary, there appears to be a single homolog recognition site localized at or near one end of each of the chromosomes. It is not known whether the homolog recognition site is associated with a centromere, but it is clear that this region is responsible for the initiation of the meiotic phenomena of homolog pairing, recombination, and proper disjunction.
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[
Methods Cell Biol,
1995]
Geneticists like to point out that the ultimate test of a proposed function for a gene and its encoded product (or products) in a living organism involves making a mutant and analyzing its phenotype. This is the goal of reverse genetics: a gene is cloned and sequenced, its transcripts and protein coding sequence are analyzed, and a function may be proposed; one must then introduce a mutation in the gene in a living organism to see what the functional consequences are. The analysis of genetic mosaics takes this philosophy a step further. In mosaics, some cells of an individual are genotypically mutant and other cells are genotypically wild type. One then asks what the phenotypic consequences are for the living organism. This is not the same as asking what cells transcribe the gene or in what cells the protein product of the gene is to be found, but rather it is asking in what cells the wild-type gene is needed for a given function...
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[
1971]
This review deals with the biological and physiological characteristics of the Nematoda which may be of significance in studies of biological aging. In general, the discussion is confined to soil-inhabiting nematodes, but supporting evidence is drawn from studies of animal parasitic forms and other kinds of organisms.
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[
WormBook,
2007]
It is now well established that cells modify chromatin to establish transcriptionally active or inactive chromosomal regions. Such regulation of the chromatin structure is essential for the proper development of organisms. C. elegans is a powerful organism for exploring the developmental role of chromatin factors and their regulation. This chapter presents an overview of recent studies on chromatin factors in C. elegans with a description of their key roles in a variety of cellular and developmental processes.
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[
1960]
For the purpose of the present chapter the noun 'cultivation' is to be taken as the maintenance, in the laboratory, of a population of organisms belonging to a desired species through successive generations and subcultures over a prolonged period of time (weeks, months, or years). This is a deliberate restriction of the term. The noun 'culture' is most aptly used for a population within a circumscribed vessel or container (test-tube, Petri dish, U.S. Bureau of Plant Industry watch glass, etc.); it is also used in a looser, more general way (as "in culture") to cover conditions of substantial growth whether or not leading to cultivation in the strict sense