Chip Technologies, Basic Principles

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C Type Lectin Domain Definition C type lectin domains are involved in calcium dependent carbohydrate recognition. ▶Autosomal Dominant (Inherited Disorder) ▶Polycystic Kidney Disease, Autosomal Dominant

C. Elegans ▶Caenorhabditis elegans as a Model Organism for Functional Genomics ▶C. elegans Genome, Comparative Sequencing

C. elegans Genome, Comparative Sequencing J AGAN S RINIVASAN , R ALF J. S OMMER Max Planck Institute for Developmental Biology, Department of Evolutionary Biology, Tübingen, Germany [email protected]

Definition Caenorhabditis elegans (C. elegans) is a small, freeliving nematode found commonly in many parts of the world. It is 1 mm long and has a life cycle of 3–4 days at 20°C. C. elegans is a bacteriovore and feeds mainly on Escherichia coli under laboratory conditions. It exists as two sexes, as hermaphrodites and males. The hermaphrodite produces both sperm and oocytes and reproduces by self-fertilisation. Spontaneous males are very rare and occur at a frequency of 10–3 to 10–4. During its reproductive life span, a hermaphrodite lays around 300 eggs. This number is controlled since

sperm is the limiting factor during self-fertilisation. Freshly hatched eggs undergo four larval stages (L1– L4), punctuated by moults. The adult arising after the fourth larval moult is reproductively mature for about four days and lives for an additional ten days.

Characteristics The success of the worm as a model system in modern biology lies in its easy amenability under laboratory conditions and its simple anatomical architecture. C. elegans is made up of a relatively small number of cells and the cell lineage is invariant, that is, it is identical from individual to individual. Specifically, the adult hermaphrodite has 959 cells and the adult male has 1031 cells. The development of all of these cells is known and can be studied by differential interference contrast (DIC) microscopy. Pioneering work during early phases of C. elegans research led to the complete description of the cell lineage and the determination of the connectivity of the nervous system (1). To test functional aspects of the cell lineage and potential cellcell interactions two approaches are used. First, by laser microbeam irradiation, individuals cells can be deleted from living animals and the consequences of these “cell ablations” be investigated during the further development of the individual. Second, mutants can be obtained following chemical mutagenesis or exposure to ionising radiation (2). C. elegans possesses six linkage groups (5 autosomes and 1 sex chromosome) with each linkage group having a genetic size of 50 cM. The physical size of the genome is 100 Mb. Together, the small genome size, the rapid generation time, the invariant cell lineage and the ability to generate mutants made C. elegans a popular model system for developmental genetics. Further research in C. elegans focussed on getting a molecular understanding of the vast diversity of mutants isolated in various genetic screens. These studies were accelerate

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