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Creatures line up to be sequenced

February 28, 2004 By Helen R. Pilcher This article courtesy of Nature News.

Researchers set sights on opossum genome.

Researchers in the US have lined up the next set of creatures to have their genomes sequenced. The lucky crew makes for an odd menagerie: in the queue is an opossum, four fungi, three roundworms and a beetle.

The grey short-tailed South American opossum has the added honour of being the first marsupial to have its genetic code cracked.

The new recruits will join an elite club, which boasts members such as the human, mouse, honeybee and fruit fly, among others. By comparing the genomes of such species we hope to learn more about human development and disease.

"Comparing the human genome sequence with those of other organisms allows us to identify regions of similarity and difference, providing critical clues about the structure and function of human genes," says Francis Collins, director of the National Human Genome Research Institute in Bethesda, Maryland.

"It will also help us understand the mechanisms that control gene expression," says Tim Hubbard who runs the human genome analysis group at the Sanger Centre in Cambridge. This will help explain how, when and where genes are turned on and off.

The work will begin this year in five National Institutes of Health-funded research centres in the US.

In the meantime, work continues to finish the sequences of several other animals already in the pipeline. These include the purple sea urchin, the rat, the chimp, and the humble cow.

With good reason

The South American opossum joins the shortlist because of its special position in the evolutionary tree.

Opossums and humans diverged from a common ancestor around 130 million years ago - roughly 55 million years before mice went their separate way, but 200 million years after birds branched out.

"The opossum evolved at an interesting point in the evolutionary time-line," says Hubbard. It may be able to tell us something about the evolutionary process, he adds.

The marsupial will also help researchers study the early stages of development. Opossums are born after a gestation period of just 12 days. The blind, bald babies crawl into their mother's protective pouch to complete their development. This makes them readily accessible for medical research.

Opossums also provide a good model of melanoma, the most deadly form of skin cancer. They are the only laboratory animal known to develop melanoma after exposure to UV radiation alone. Armed with knowledge of their genome, researchers may be able to unravel the molecular basis of melanoma and explore new treatments.

As for the other creatures, the primitive genomes of fungi should offer insight into basic biological processes that have remained unchanged throughout evolution.

Knowledge of the genetic makeup of the red flour beetle could help researchers devise ways to curb the pest's voracious appetite for grain and cereal.

The roundworm, an organism that can regenerate its entire body from a severed section, should help researchers seeking to understand tissue regeneration.


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