In Australia, the cane toad ( Bufo marinus) species was introduced in 1935 to control cane insect pests. This experiment paved the way for what we know today as the field of cloning. Nuclear transfer is an embryological technique, and involves removal of the nucleus from an egg and replacement with the nucleus of another donor cell. The Leopard frog ( Rana pipiens) in 1952 became the first successful nuclear transfer experiment. This animal model has also shown that localization of maternal messenger RNA (eg vegetal and review) appears to play a key role in the development of early embryological patterns. You can see an overview of the frog life cycle with links to specific stages as well as movies of the early process of gastrulation. The advantages of this frog is the fertility cycle can be easliy controlled and the eggs develop entirely independently and easily visible to the investigator. The African clawed frog ( Xenopus laevis) has been used in many embryological and electrophysiological studies as well as the basis of a historic pregnancy test. The 2012 Nobel prize in medicine was recently awarded to John Gurdon for his 1960's experiments involving nuclear transplantation with adult nuclei into frog eggs, these studies were the precursor to current research in stem cells. The frog was historically used by many of the early embryology investigators and currently there are many different molecular mechanisms concerning development of the frog. There have also been many different species used in these developmental studies. The later metamorphosis of the tadpole to frog has also been studied for hormonal controls and limb development. The frog has been historically been used as an amphibian animal model of development due to the ease of observation from the fertilized egg through to tadpole stage. Hans Spemann discoverer of the organiser region (primitive node) for gastrulation.
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