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Nature,
1991]
Stroking tiny worms with an eyebrow hair might seem an unlikely way to embark on the study of neuronal degeneration, but two reports on touch sensitivity in the nematode Caenorhabditis elegans (one of which appears on page 588 of this issue) provide impressive case studies of the pathological degeneration and death of identified neurons. These studies define two members of a new gene family, called 'degenerins', which can undergo mutation and cause the deterioration of certain nerve cells. The degenerin genes seem to exhibit some phylogenetic conservation and could therefore turn out to be involved in neuronal degeneratin in mammals as well as in nematodes.
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Nature,
1990]
Fruitflies and nematodes show many similarities in the general organization of the gene networks that control sexual dimorphism and dosage compensation. In contrast, the underlying molecular mechanisms appear to be very different in these two species. Developmental processes such as sex determination need not be strongly conserved in evolution.
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International Journal of Developmental Biology,
1998]
Pleiotropy , a situation in which a single gene influences multiple phenotypic tra its, can arise in a variety of ways. This paper discusses possible underlying mechanisms and proposes a classification of the various phenomena involved.
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Cell,
1999]
Cell death in universally important in development, not the least in the nervous system, but little is known about how the programmed cell deaths of cells and neurons are ultimately controlled. Much of the understanding of cell death has come from research on the nematode Caenorhabditis elegans (reviewed by Metzstein et al., 1998). Conradt and Horvitz (1999 [this issue of Cell]) now extend this work to provide a satisfyingly complete explanation for the sex-specific death of one particular neuron type in this animal. In so doing, they link up two extensively studied regulatory pathways in C. elegans, one controlling sexual phenotype, and one controlling cell death.
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Science,
1998]
This special issue of Science celebrates a landmark in biology:: determination of the essentially complete DNA sequence of an animal genome. The animal is a small invertebrate, the nematode (or roundworm) Caenorhabditis elegans, and the sequence consists of about 97 million base pairs of DNA, approximately one-thirtieth the number in the human genome. Nonetheless, the information content is enormous - eight times that of the budding yeast Saccharomyces cerevisiae, the only other eukaryote with a sequenced genome.
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[
Seminars in Developmental Biology,
1992]
The nematode Caenorhabditis elegans has two natural sexes, the self-fertilizing hermaphrodite (essentially a modified female) and the male. Sex is determined by X chromosome dosage: hermaphrodites are XX, males are XO. This primary signal sets the state of activity for a series of regulatory genes, which are organized hierarchically. The genes at the top of the hierarchy control both sex and dosage compensation; genes acting lower down in the hierarchy control sexual phenotype in both soma and germ-line, but do not affect dosage compensation. Regulation of sexual phenotype is somewhat different between soma and germ line. Many of the genes involved in sex determination have been subjected to molecular analyses. The results indicate that some of the regulatory interactions involve transcriptional controls and others
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[
Trends In Genetics Genetic Nomenclature Guide,
1995]
This summary is based on the original proposals for C. elegans nomenclature, plus additional recommendations that have been distributed in the Worm Breeder's Gazette.
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[
Neuron,
1991]
Most animal species occurr in two different sexual forms, which usually exhibit a substantial degree of dimorphism in behavior. Often the most elaborate patterns of activity displayed by an animal are sex-specific behaviors such as courtship, mating, nest-building, and so forth. A vast literature exists on every aspect of sex-specific behavior, reporting observations on a great variety of different animal types. The questions addressed by these studies reange across the whole of biology, from ethology to crystallography. The present review is concerned with a limited part of this subject, the molecular basis of sex-specific development in the nervous systems, and will focus on systems in which it is becoming possible to define precise genetic and cellular mechanisms. This means concentrating primarily on two invertebrates, the nematode Caenorhabditis elegans and the fruitfly Drosophila melanogaster, and on a few mammalian and avian species.
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[
Trends in Genetics,
1987]
Suppressor mutations (both dominant and recessive) are easily obtained in Caenorhabditis elegans, as a result of efficient selection methods and the ability to grow large populations by self-fertilization. Several different genetic phenomena are revealed by the study of suppression. A set of five amber suppressors is being used to analyse a family of tRNA genes.