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[
1992]
Caenorhabditis elegans is a small soil nematode which is currently being extensively studied to discern general principles of how genes control development. The short life cycle, ability to culture in quantities sufficient for biochemical work, well-developed genetics, small cell number for a rather sophisticated animal, and rapidly increasing possibilities for molecular genetics are features that make this species a very productive system
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[
WormBook,
2006]
Through genetic analyses, the function of genes is investigated by studying organisms where gene function is altered. In classical forward genetic screening, individuals are treated with mutagens to induce DNA lesions and mutants with a phenotype of interest are sought. After a mutant is found, the gene mutated is identified through standard molecular techniques. Detailed studies of the mutant phenotype coupled with molecular analyses of the gene allows elucidation of the gene's function. Forward genetics has been responsible for our understanding of many biological processes and is an excellent method for identifying genes that function in a particular process.In reverse genetics, the functional study of a gene starts with the gene sequence rather than a mutant phenotype. Using various techniques, a gene's function is altered and the effect on the development or behaviour of the organism is analysed. Reverse genetics is an important complement to forward genetics. For example, using reverse genetics, one can investigate the function of all genes in a gene family, something not easily done with forward genetics. Further, one can study the function of a gene found to be involved in a process of interest in another organism, but for which no forward genetic mutants have yet been identified. Finally, the vast majority of genes have not yet been mutated in most organisms and reverse genetics allows their study. The availability of complete genome sequences combined with reverse genetics can allow every gene to be studied.This chapter gives detailed protocols for the two main methods of perturbing gene function in C. elegans: RNA interference and the creation of deletion mutants. Either technique can be applied to the study of individual genes. With less than a day of actual work, RNAi creates a knockdown of gene function without altering the organism's DNA (see below). In contrast, with about a month of work, a deletion mutation permanently removes all gene function. Deciding which technique to use will depend on the nature of the experiment. The techniques can also be combined, where RNAi is used for rapid screening of loss of function phenotypes and then deletion mutants are made to study genes of particular interest. RNAi can also be carried out on a global scale, where knockdown of (nearly) every gene is tested for inducing a phenotype of interest. In this case, the reverse genetics technique of RNAi can be thought of as a forward genetic screening tool.
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[
WormBook,
2007]
Strongyloides is a genus of parasitic nematodes, which, unusually, has a free-living adult generation. Here we introduce the biology of this genus, especially the fascinating, but complex, life-cycle together with an overview of the taxonomy, morphology, genetics and genomics of this genus.
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[
Methods Enzymol,
2011]
Most serpins inhibit serine and/or cysteine proteases, and their inhibitory activities are usually defined in vitro. However, the physiological protease targets of most serpins are unknown despite many years of research. This may be due to the rapid degradation of the inactive serpin:protease complexes and/or the conditions under which the serpin inhibits the protease. The model organism Caenorhabditis elegans is an ideal system for identifying protease targets due to powerful forward and reverse genetics, as well as the ease of creating transgenic animals. Using combinatorial approaches of genetics and biochemistry in C. elegans, the true in vivo protease targets of the endogenous serpins can be elucidated.
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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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[
2003]
Since the publication of the first genetic research paper on Caenorhabditis elegans (C. elegans for short) in 1974, this microscopic, free-living nematode has become a popular model organism to study development, neurobiology, and other biological problems. The ability to do powerful genetics has been the most critical reason why studies using this organism have made enormous contributions to basic biology and medical science. Therefore, C. elegans genetics should be part of any modern genetic education. In this chapter, we describe some of the unique properties of C. elegans that makes it an exceptional organism for genetic and molecular biological research. Some important genetic tools and methodologies developed by C. elegans researchers will also be introduced. We aim to connect the fundamental principles of genetics as described in early chapters with practical applications of these principles in actual research. We have chosen a few genetic pathways and biological problems as examples for illustrating the logic behind the genetic analyses and for introducing some commonly practiced strategies and methods. We do not hesitate to introduce some of the most advanced and up-to-date methods and approaches, including those developed since the genome sequence was determined in 1998. We believe today's students can go right into the heart of present research after learning the basic principle of Genetics (see the early chapters of this book) and molecular biology. In fact, in many C. elegans laboratories, undergraduate students are doing a wide variety of experiments using the genetic techniques
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[
WormBook,
2006]
In the last decade, nematodes other than C. elegans have been studied intensively in evolutionary developmental biology. A few species have been developed as satellite systems for more detailed genetic and molecular studies. One such satellite species is the diplogastrid nematode Pristionchus pacificus. Here, I provide an overview about the biology, phylogeny, ecology, genetics and genomics of P. pacificus.
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[
1975]
Studies in behaviour genetics have covered a wide field: motivation, development, sensory capacities, intelligence, learning, evolution, neuromorphology and neurochemistry have all been approached using genetic techniques, and there are probably others. Whilst it is at present impossible to construct any unities one must accept that many such studies have as their common aim one of the most fundamental problems in biology: how is behavioral potential encoded in genetic terms and expressed in the course of development? The relative enormity of this problem is often matched by its inaccessibilty. It cannot be claimed that there is any agreed view of the way forward and much of the work has frankly to be opportunistic-seizing on some favourable material or a useful new analytical technique to gain a limited objective. Consequently, behaviour genetics often presents a confusing picture of numerous disjointed studies, with
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[
Modeling in Molecular Biology. G Ciobanu and G Rozenberg (eds). Natural Computing Series, Springer-Verlag.,
2004]
We present preliminary results of a new approach to the formal modeling of biological phenomena. The approach stems from the conceptual compatibility of the methods and logic of data collection and analysis in the field of developmental genetics with the languages, methods and tools of scenario-based reactive system design. In particular, we use the recently developed methodology consisting of the language of live sequence charts with the play-in/play-out process, to model the well-characterized process of the cell fate acquisition during C. elegans
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[
WormBook,
2007]
Acetylcholine is the major excitatory neurotransmitter at nematode neuromuscular junctions, and more than a third of the cells in the C. elegans nervous system release acetylcholine. Through a combination of forward genetics, drug-resistance selections, and genomic analysis, mutants have been identified for all of the steps specifically required for cholinergic function. These include two enzymes, two transporters, and a bewildering assortment of receptors. Cholinergic transmission is involved, directly or indirectly, in many C. elegans behaviors, including locomotion, egg laying, feeding, and male mating.