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African clawed frog

2007 Schools Wikipedia Selection. Related subjects: Insects, Reptiles and
Fish

               iAfrican clawed frog

                             Conservation status

   Least Concern (LC)
            Scientific classification

   Kingdom: Animalia
   Phylum:  Chordata
   Class:   Amphibia
   Order:   Anura
   Family:  Pipidae
   Genus:   Xenopus
   Species: X. laevis

                                Binomial name

   Xenopus laevis
   Daudin, 1802

   The African clawed frog (Xenopus laevis, also known as platanna) is a
   species of South African aquatic frog of the genus Xenopus. It is up to
   12 cm long with a flattened head and body but no tongue. Its name
   derives from its three short claws on each of its hind feet, which it
   probably uses to stir up mud to hide it from predators.

   Although X. laevis is not blessed with the short generation time and
   genetic simplicity generally desired in genetic model organisms, it is
   an important model organism in developmental biology. X. laevis takes 1
   to 2 years to reach sexual maturity and, like most of its genus, it is
   tetraploid. However, it does have a large and easily manipulable
   embryo. The ease of manipulation in amphibian embryos has given them an
   important place in both historical and modern developmental biology. A
   related species, Xenopus tropicalis, is now being promoted as a more
   viable model for genetics. Roger Wolcott Sperry used X. laevis for his
   famous experiments describing the development of the visual system.
   These experiments led to the formulation of the Chemoaffinity
   hypothesis.

   Xenopus oocytes provide an important expression system for molecular
   biology. By injecting cDNA or cRNA into the developing oocyte,
   scientists can study the protein products in a controlled system. This
   allows rapid functional expression of manipulated cDNAs (or cRNA). This
   is particularly useful in electrophysiology, where the ease of
   recording from the oocyte makes expression of membrane channels
   attractive. One challenge of oocyte work is eliminating native proteins
   that might confound results, such as membrane channels native to the
   oocyte. Translation of proteins can be blocked or splicing of pre-mRNA
   can be modified by injection of Morpholino antisense oligos into the
   oocyte (for distribution throughout the embryo) or early embryo (for
   distribution only into daughter cells of the injected cell).

   X. laevis is also notable as having been a standard method of pregnancy
   testing. Human chorionic gonadotropin is a hormone found in substantial
   quantities in the urine of pregnant women; when injected into the
   female X. laevis it induces them to lay eggs.

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