ABSTRACT
The free living nematode Caenorhabditis elegans was chosen by Sydney Brenner in 1965 as a model animal to study development and the nervous system. Genetic transformation consists in introducing, maintaining and expressing an extra piece of DNA in the whole organism. It provides a powerful functional test of gene activity in vivo. Microinjection in C. elegans germline was first carried out by Kimble et al. who rescued a nonsense mutation by injection of suppressor tRNA in the syncytial gonad. Stinchcomb et al. showed that injected DNA could be maintained in transgenic lines as extrachromosomal arrays. Wild type cloned genes selected by their ability to rescue the corresponding recessive visible mutants are also used as cotransformation markers. Only mosaic analysis allows defining the cells in which gene expression is both necessary and sufficient for the animal to display a wild type phenotype.
