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What can a sea urchin tell us about having a backbone?

Scientists have begun to unravel the genome the chemical instructions for life contained in an organism's every cell for the purple sea urchin, Strongylocentrotus purpuratus.

A large group of researchers led by George Weinstock of Baylor College of Medicine presents the sea urchin genome sequence in a special issue of the 3 November 2006 issue of the journal Science.

The sea urchin is one of biologists' most beloved "model" animals, meaning researchers study it to learn about processes that happen in the bodies of many different kinds of animals.

It may not look like it on the outside, but these spiky animals that slowly inch along the seafloor are more closely related to humans and other vertebrates than fruit flies or roundworms. These two animals are also popular model organisms whose genomes have been sequenced.

Sea urchins belong to the phylum "Echinodermata," which includes starfish and sea cucumbers. Humans belong to the phylum "Chordata," which includes all animals with backbones. Both the echinoderms and chordates belong to a larger group called the "deuterostomes."

The sea urchin is the first deuterostome animal outside of the chordate group to have its genome sequenced. So, scientists will now be able to compare the DNA instructions that produce the sea urchin with those that produce a chordate, such as a human. This should help us understand exactly what it takes to build the features that we share with our close relatives, such as backbones.

Scientists also use model organisms to study diseases and possible treatments. The sea urchin contains a large number of genes that are also linked to human diseases, and its genome sequence may now help researchers learn about human health.

Sea urchins have a long history of helping biologists make important discoveries. A century ago, scientists discovered the how fertilization works by studying sea urchins. They also figured out that the complete genome (contained in structures called chromosomes) must be present in every cell of an embryo for it to develop normally.