Scientists Give Extinction the Cold Shoulder : Wildlife: DNA from endangered animals is frozen to allow for species to be bred later. Technology includes an antifreeze for cells.


Betsy Dresser and her colleagues at the Cincinnati Zoo are using DNA to keep endangered animals from going the way of the dinosaur.

They freeze embryos, sperm and eggs from endangered animals as a safety net against extinction.

"If scientists had been around with this technology when the dinosaurs were here, we could indeed bring them back," said Dresser, director of research at the zoo's Center for Reproduction of Endangered Wildlife.

About 90% of every cell is made of water. When an embryo is removed from a female animal, the water is extracted and replaced with a cryoprotectant--an antifreeze for cells.

Embryos prepared like this can be frozen and kept alive for thousands of years, if necessary, Dresser said. The embryos can then be thawed and implanted in a surrogate animal for breeding.

The difference between what Dresser is doing and what the scientists in the movie "Jurassic Park" did is the difference between living and dead DNA.

"When you've got frozen embryos, you've essentially got living DNA," she said. "If you can thaw them out and find a surrogate, you can keep species from going extinct."

In the movie, DNA was extracted from dinosaur blood found in prehistoric mosquitoes preserved when they got stuck in tree resin.

Because the DNA wasn't frozen, it was no longer viable. The movie scientists essentially bring the dead back to life by combining the dead DNA with live DNA from frogs.

"We don't know today what it is that triggers the (dead) DNA on," Dresser said.

But scientists eventually may figure it out. She said she has learned in her career not to dismiss anything as too "sci-fi."

The cattle industry has been using the embryo transfer process for about 40 years. But only in the last decade or so have scientists used the technology to breed exotic animals.

Dresser is among the pioneers in frozen technology, said Michael Hutchins, director of conservation and science of the American Assn. of Zoological Parks and Aquariums, based in Bethesda, Md.

The association represents 160 zoos and aquariums in the United States and Canada--including the Cincinnati Zoo--that have a breeding program for 67 endangered species.

Zoos in San Diego; Omaha, Neb.; Washington, and London are doing research similar to Dresser's work, Hutchins said.

Dresser's center has achieved several firsts, including the birth of an eland antelope from a previously frozen embryo and interspecies embryo transfer--an endangered Indian desert cat was born to a domestic cat.

At the moment, the research center has frozen embryos, sperm and eggs representing about 500 species. The embryos represent only nine species.

But there's room to grow. The 4-by-2-foot storage tank filled with liquid nitrogen can hold 10,000 embryos. Such a frozen zoo would represent more animals than in almost all zoos combined, Dresser said.

The center also has a frozen garden of germ plasma, or reproductive cells, of exotic and endangered plants, that can be used to clone plants in test tubes.

Dresser said she is not concerned that some might think she is tampering with evolution.

"We can't keep up with the damage that man is doing to the planet," she said. About 100 species become extinct every day, she said.

But Thomas Long, an associate professor of philosophy at the University of Cincinnati who specializes in bioethics, said the ethics of biotechnology must be a consideration.

"Is the technology to benefit the animal species in the long run, or is it an attempt to benefit human beings?" Long asked.

Long said it may not necessarily be a good thing to protect a species from extinction.

"Nature has eliminated untold numbers of species for various reasons, such as they didn't work," he said. "Take dinosaurs, for example."

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