Caenorhabditis elegans

minuscule worm whose entire genome has recently been decoded and mapped (joint work of American and British teams)

Caenorhabditis elegans (IPA: ) is a free-living nematode (roundworm), about 1 mm in length, which lives in temperate soil environments. Research into the molecular and developmental biology of C. elegans was begun in 1974 by Sydney Brenner  and it has since been used extensively as a model organism.
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A normally self-fertilizing hermaphrodite soil nematode whose developmental genetics has been extensively studied. It is no more than 1 mm long. Loss of an X chromosome by meiotic disjunction leads to the production of males. The genetic basis of apoptosis was first shown in C.elegans in 1986. It has five equally sized chromosomes and it is the first animal whose whole genome has been sequenced (in 1998). The 97 Mbp genome contains 19,000 genes on 6 chromosomes. About 74% of human genes have their homologues in the C.elegans genome. Links to the C.elegans website and an intoduction to C.elegans.