Frogs have served as important model organisms throughout the history of science. Eighteenth-century biologist Luigi Galvani discovered the link between electricity and the nervous system through studying frogs. The African clawed frog or platanna, Xenopus laevis, was first widely used in laboratories in pregnancy assays in the first half of the 20th century. When human chorionic gonadotropin, a hormone found in substantial quantities in the urine of pregnant women, is injected into a female X. laevis, it induces them to lay eggs. In 1952 Robert Briggs and Thomas J. King cloned a frog by somatic cell nuclear transfer, the same technique that was later used to create Dolly the Sheep, their experiment was the first time successful nuclear transplantation had been accomplished in metazoans.^[1] Distribution of frogs (in black) Suborders Archaeobatrachia Mesobatrachia Neobatrachia - List of Anuran families A frog is an amphibian in the order Anura. ... Luigi Galvani Luigi Galvani (September 9, 1737–December 4, 1798) was an Italian physician and physicist who lived and died in Bologna and who discovered that muscle and nerve cells produce electricity. ... Lightning strikes during a night-time thunderstorm. ... The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. ... 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. ... Human chorionic gonadotropin (hCG) is a peptide hormone produced in pregnancy, that is made by the embryo soon after conception and later by the trophoblast (part of the placenta). ... A hormone (from Greek horman - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ... Urine is liquid waste excreted by the kidneys and is produced by the process of filtration. ... An average Whooping Crane egg is 102 mm long, and weighs 208 grams In some animals, an egg (Latin ovum) is the zygote, resulting from fertilization of the ovum. ... Thomas J. King (1921 - October 25, 2000) was an American biologist. ... In genetics, somatic cell nuclear transfer (SCNT) is a technique for cloning. ... Dolly and her first-born lamb, Bonnie Dolly (5 July 1996 – 14 February 2003), a ewe, was the first mammal to have been successfully cloned from an adult cell. ...

Frogs are used in cloning research and other branches of embryology because frogs are among the closest living relatives of man to lack egg shells characteristic of most other vertebrates, and therefore facilitate observations of early development. Although alternative pregnancy assays have been developed, biologists continue to use Xenopus as a model organism in developmental biology because it is easy to raise in captivity and has a large and easily manipulatable embryo. Recently, X. laevis is increasingly being displaced by its smaller relative X. tropicalis, which reaches its reproductive age in five months rather than one to two years (as in X. laevis),^[2] facilitating faster studies across generations. The genome sequence of X. tropicalis will probably be completed by 2015 at the latest.^[3] Embryology is the branch of developmental biology that studies embryos and their development. ... A model organism is a species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. ... Developmental biology is the study of the process by which organisms grow and develop. ... Genome projects are scientific endeavours that aim to map the genome of a living being or of a species (be it an animal, a plant, a fungus, a bacterium, an archaean, a protist or a virus), that is, the complete set of genes caried by this living being or virus. ...

References

1. ↑ http://newton.nap.edu/html/biomems/rbriggs.html
2. ↑ Developing the potential of Xenopus tropicalis as a genetic model. (HTML) URL accessed on 2006-03-09.
3. ↑ Joint Genome Institute - Xenopus tropicalis Home. (HTML) URL accessed on 2006-03-03.