Xenopus (L., strange foot) are a genus of carnivorous frog native to Africa. There are 15 species in the Xenopus genus, all aquatic with unwebbed fingers and fully webbed feet, with claws on three toes. The best-known species belonging to this genus is Xenopus laevis, which is commonly studied as a model organism.
Xenopus are a popular model system for gene and protein expression and knockdown studies. At 1 mm diameter, Xenopus oocytes are very large cells which are easy for scientists to culture and use in experiments. RNA from other organisms can be injected into the large oocytes and the resulting expression studied via molecular biology techniques or through electrophysiology experimentation. Gene expression can be knocked down or splicing modified using Morpholino antisense oligos injected into Xenopus oocytes (for whole-body effects) or early embryos (for effects in the daughter cells descended from the injected cell). Cytoplasmic extracts made by centrifuging Xenopus eggs or embryos (allowing direct addition or depletion of proteins) can recapitulate a wide range of complex cellular processes including nuclear envelope formation, DNA replication and spindle assembly.
While Xenopus laevis is the most commonly used species for developmental biology studies, genetic studies can be complicated by their pseudotetraploid genome. Xenopus tropicalis provides a simpler model for genetic studies, having a diploid genome. Morpholino knockdown techniques are also used in X. tropicalis to probe the function of a protein by observing the results of eliminating the protein's activity, as was done in a screen of X. tropicalis genes published in 2006.
X. laevis is often used as a low-tech pregnancy test; for details, see the species account.