UC Santa Cruz could someday house the world's largest zoo — holding not live animals but the genetic codes of 10,000 creatures, many of them exotic or extinct.

The ambitious quest, led by some of the nation's top geneticists and unveiled Wednesday morning, for the genetic codes would cost $50 million and take a lifetime to achieve.

But the computer-based conservatory — called "Genome 10K Project" — would transform biology, building a digital record of molecular triumphs and stumbles across 500 million years of evolutionary history.

Although currently just an unfunded proposal, the global database eventually could help humans by unraveling biological mysteries, such as why we live only eight decades while other creatures, such as the bowhead whale, live for two centuries. Genome comparisons also could change long-held taxonomical assumptions and assist species conservation.

"We can now contemplate reading the genetic heritage of all species, beginning with vertebrates," said UCSC biomolecular engineer David Haussler, a chief architect of the project.

Evoking writer Rudyard Kipling, he said, "We hope to learn how the elephant got its trunk, how the leopard got its spots."

The 54-page proposal is described in today's issue of the Journal of Heredity. More than 65 other scientists, including some from UC Berkeley, the federal Laboratory of Genomic Diversity and the San Diego Zoo, have joined the project.

In

many ways, the plan is not so far-fetched. Naturalists in jungles, deserts and other far-flung habitats have been busy collecting tissue samples from the animal kingdom — more than 16,000 species, at last count. This collection, stored for posterity, spans mammals, birds, reptiles, amphibians and fish. And Rockefeller University's Barcode of Life Initiative is also using genetics to inventory creatures, but it uses a short gene sequence to help identify creatures instead of the full genome.

Meanwhile, the cost of sequencing — now $50,000 to $100,000 per genome — is plummeting. When it hits $3,000, "We'll be good to go," said Haussler.

UC Santa Cruz is already home to the Genome Browser, which offers free public access to the genetic blueprints of humans and 45 animals, including the extinct woolly mammoth and Tasmanian tiger.

The Genome 10K Project would build upon this existing Browser database and enhance "The Encyclopedia of Life," a Harvard-Smithsonian collaboration that is creating multimedia wiki-style Web pages for all 1.8 million species.

But the project will demand a mind-numbing amount of computational power, far more than currently available. Billions of letters of digital information would be stored, then analyzed.

The project was launched at a three-day meeting at UCSC in April . At this gathering, scientists from 55 major zoos, museums, research centers and universities debated the logistics of the challenge.

One of the meeting's rules: "No one was allowed to argue that 'My species is better than your species,'" joked Haussler.

Another rule: Only vertebrates, those 58,000 species with backbones or spinal columns, would be considered — leaving for future generations the job of decoding the genomes of an estimated 1.8 million species of flowers, fungi and other forms of life.

The Genome 10K Project scientists predict many similarities will be found in the sequences because all vertebrates share a core repertoire of genes.

What they are interested in are the differences: those mutations that led to great biological events of the past, such as the development of wings, fins, arms, the four-chambered heart and color vision.

The historical record will help answer other questions too, such as: When did humans start bearing live offspring rather than laying eggs? When did we emerge from water — and why, in four instances, did we return? How did wings evolve? When did we gain a pancreas?

"The most challenging intellectual problem in biology for this century will be the reconstruction of our biological past," said Nobel Laureate Sydney Brenner of the Salk Institute, one of proposal's authors. "Genomes are molecular fossils."

Working backward, it could be possible to reconstruct — at least, within a computer — the common ancestor of all mammals: a shrewlike creature that scurried around with the dinosaurs at the time of the Cambrian explosion of animal life.

Perhaps the information could help with conservation, if genes can predict how an animal will respond to climate change, pollution, invasive competitors and emerging diseases.

For instance, perhaps some amphibians carry genes that protect against a deadly fungus that is now erasing frog populations around the world.

It is certain to reveal the shrunken and inbred gene pools of small populations of endangered species.

"The risk of extinction is lessened for species for which we have a genome sequence, because it enables studies," said Oliver A. Ryder, director of genetics at the San Diego Zoo and a co-author of the proposal.

Genes can't be used, like Tinker Toys, to build extinct animals from scratch. But scientists believe that sequences could provide a recipe for how rebreed, using selective techniques, long-gone creatures such as dodo birds, passenger pigeons or the Tasmanian tiger.

"Genetic variation has created such stunningly specific and beautiful life forms," said Haussler. "How did that happen? We want to understand it."

Reach Lisa M. Krieger at 408-920-5565.