General Characteristics of Nematodes
Nematodes are roundworms and are generally considered to be the most numerous multi-cellular organisms on Earth, having adapted to nearly every possible ecological niche, from the frozen wastes of Antarctica to the bottom of the ocean and many points in between.
C. elegans is a free-living soil-dwelling nematode worm, that’s about 1mm in length, and holds the honour of being the first multi-cellular organism to have its genome mapped. It contains 97 million base pairs consisting of around 20,000 genes, many of which have functional counterparts in humans. And there isn’t a female sex; just hermaphrodites and males.
The scientist has a number of model organisms to choose from including knockout mice, E.coli, and the fruit fly drosophila melanogaster. C. elegans is a relative late comer on the lab scene having being plucked from obscurity in 1960s by the biologist Sydney Brenner who used it as a model organism to study the role of genes in development. And since then there has been no turning back. C. elegans is a beneficial nematode for scientists for a number of reasons: -
C. elegans can be handled like a microbe - Large numbers of worms can be maintained cheaply and they can feed off bacterial mats grown on agar plates. C. elegans can be stored frozen and still be viable when thawed.
Short life cycle - C. elegans has a two week life cycle making it ideal for genetic analysis, and to follow what happens down the generations.
C. elegans is transparent - it stays transparent throughout its life, facilitating observations of cellular processes and the effects of gene expression.
Cell fate - there are approximately 1,000 somatic cells and their developmental fate has been completely mapped out. Contrast this to the cell fate in many higher organisms where cellular cues play a large part in development. Every cell can be traced back to the egg. The cells divide and specialise in a typical way so that every adult worm has the same number of cells which are arranged in the same manner - 959 in the adult hermaphrodite and 1031 in the adult male.
Simple nervous system - C. elegans happens to be one of the simplest organisms with a nervous system. There are 302 neurons and these have been completely mapped.
Similarity to humans - C.elegans and humans share many genes and molecular pathways. For example the insulin signalling pathway is one of the many whole pathways that have been conserved between worm and human. This makes C.elegans a superb model for human diseases.
Therapeutic testing - mutations can easily be generated to create disease-like conditions. These can be subject to many potential therapeutics to see which ones return the nematode to its normal disease-free state.
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