Cloning: good science or baaaad idea: (includes a comparison of reproduction of sheep by fertilization and by cloning)(Cover Story)
Meanwhile, a third Bill Clinton is out playing golf, while a fourth is helping daughter Chelsea with a science project.
Sound far-fetched? That day may come. Scientists in Scotland recently announced that, for the first time, they have cloned an exact copy of an adult mammal. The cloned baby lamb, named Dolly, has the exact same genes as the adult sheep from which she was cloned. In other words, the two are identical twins; only Dolly is six years younger. The goal of embryologist Ian Wilmut, the lead scientist, is to develop a way to raise identical sheep that produce medications for humans.
A week after Wilmut's announcement, scientists in Oregon disclosed that they had used a different technique to clone rhesus monkeys, primates that are close cousins of humans. Faster than you can say "Frankenstein," these accomplishments triggered a worldwide debate: Should scientists be allowed to clone animals? Will humans be next? Is cloning unethical and dangerous--or is it a valuable research tool? Read about the latest cloning techniques; then debate and decide.
All attempts at cloning were largely unsuccessful until 1984. That's when a scientist in Denmark separated cells from a sheep's embryo. An embryo is an early stage of development in which cells are busy dividing and "transforming" into specialized cells like skin, eye, or muscle cells.
Unlike a skin cell, an embryo is on its way to becoming a complete living thing. The Danish scientist combined an embryo cell with an egg cell from another sheep. He implanted the fused cell--then a newly growing embryo--into a grown female sheep. To much surprise, the embryo grew into a baby lamb. Since then, other scientists have used embryos to clone cattle, pigs, goats, rabbits--and, now, even monkeys.
So what makes Wilmut's sheep unique? Instead of using early-stage embryo cells, Wilmut used cells from the udder of an adult sheep. In theory, that's like using one of your skin cells to clone a new you!
Wilmut knew that each cell of the body contains a full set of genetic instructions--a blueprint to grow a complete individual. (The only exceptions are egg and sperm cells, each of which contains half the genes to grow a new individual.) Once cells have specialized, on their way to becoming skin or eye or udder cells, most of the genetic instructions to make a full being are turned off. Until now, scientists believed that specialized cells could not be used to form a complete organism.
Wilmut proved them wrong. He found a way to "reprogram" an udder cell and make it grow into a new cloned lamb (see miniposter, pp. 12-13). An amazing fact: Dolly has no biological father.
Wilmut's success didn't come easily. He has been studying reproductive science for more than two decades. Last year, he used embryos to successfully clone two sheep, Megan and Morag. Then he forged ahead to clone an adult sheep. But, of 277 udder cells he fused with egg cells, only 30 began to develop into embryos. He implanted 29 of those into female sheep. Only one adult gave birth to a lamb.
Other scientists have jumped in to repeat Wilmut's experiment with other animals, including cows. And that's what has scientists, animal-rights activists, politicians--even President Clinton--up in arms. How far, they wonder, will cloning go?
SEND IN THE CLONES
Wilmut maintains that cloning animals has tremendous potential for helping people. Cloned sheep, he says, could be used as living drug factories. Scientists could "engineer" sheep that produce drugs in their milk. And by altering the proteins on the surfaces of animal organs to make them more like human organs, scientists believe they may be able to create a plentiful source of organ donors for people.
Why not clone humans as organ donors? Theoretically, Wilmut says, there is no reason his techniques couldn't someday be used to clone people. Think about the possibilities: a whole team of Michael Jordans, a scientific panel of Albert Einsteins, a movie starring and co-starring Brad Pitt.
On a more serious note, some fertility specialists argue that couples who have difficulty conceiving a baby could make copies of themselves. And parents whose child has a fatal disease like cancer might be able to clone the child, creating a twin who is an exact match for bone-marrow donation.
DO YOU COPY?
But even Ian Wilmut draws the line at cloning humans. "All of us would find that offensive," he says. Several countries, including Britain, Denmark, Germany, and Australia, have outlawed all scientific work on cloning humans. The U.S. has no such law, but President Clinton has set up a panel of scientists and ethicists to study the issue. In the meantime, Clinton has imposed a ban on using Federal money to clone humans.
Humans are more than the sum of their genes, argues Mark Hanson, an ethicist at the Hastings Center, an ethics research institute in Briarcliff Manor, New York. Though they look exactly the same, clones are not necessarily carbon copies. The younger twin might grow up with different influences--say, unusual friends or special teachers. A cloned Albert Einstein might flunk physics. A cloned Madonna might sing off-key.
Say you were cloned. Would your twin live a shorter life because he or she started out with teenage genes? Scientists aren't sure. And how could you prevent someone from taking a sample of your hair and making a clone of you? Again, no solutions.
Some opponents of cloning also object to the use of animals as research tools. "Next, they'll be cloning minks and foxes to make more fur coats," says Cleveland Amory, president and founder of the Fund for Animals, an animal rights group.
What do you think? Should scientists be allowed to clone animals? How about humans? Read what other Science World readers have to say (at right). Then decide for yourself.
For more on cloning, try these Web sites:
* Roslin Institute: http://www.ri.bbsrc.ac.uk/
* Oregon Regional Primate Research Center http://www.teleport.com/-orprc/
RELATED ARTICLE: CLONING: A HISTORY
Cloning's success didn't come out of the blue. Read the main article. Then, see how nearly six decades of trial and error elapsed before one scientist got it right.
A German emrbyologist theorizes that animals could be cloned by fusing an embryo with an egg cell.
Two scientists try cloning frogs, without success.
A British scientist repeats the frog experiement. He transplants frog embryo cells into egg cless. The eggs develop into tadpoles, but then die.
Two scientists report that they've cloned mice from mouse embryo cells.
No one can repeat the mouse experiment. The cloned mice turn out be be fake.
A Danish embryologist clones sheep from early-stage embryo cells. Others later repeat his experiment using cattle, pigs, goats, rabbits, and monkeys.
A scientist at the University of Wisconsin clones calves from late-stage embryo cells.
In Scotland, scientist Ian Wilmut repeats the cow embryo experiment with sheep. He puts the embryo cells to "sleep" by starving them of nutrients. Then he fuses them with egg cells. The cells "wake up" and begin to divide like new embryo cells.
Wilmut reports using the "sleeping cell" technique to clone a baby lamb named Dolly from an adult sheep's udder cell.
RELATED ARTICLE: Have you any wool?
Scientists in favor of cloning say it could have severall benefits:
* Food and clothing Scientists could alter genes and clone farm animals that produce higher-quality and more plentiful milk, meat, eggs, and wool.
* Medicines Animals could become drug factories. Scientists could genetically engineer and clone sheep that produce medicines in their milk.
* Research tools Scientists could clone animals infected with human diseases like AIDS or cancer and test different therapies to help find cures.
* Organ donors Researchers could alter the proteins on the surfaces of animals' hearts, livers, and kidneyys to make them more like human organs. Surgeons could transplant the organs into humans with less risk of rejection.
* Species survival Biologists could clone endangered species and prevent them from becoming extinct.
Tantalizing as these applications may seem, people who oppose cloning say the practice could be disastrous for animals. For instance, say a scientist clones a herd of cattle. If the wrong virus infects one cow, the entire herd could be wiped out overnight.
The bottom line: Dolly the sheep may be a first step, but scientists have a lot to learn.
|Printer friendly Cite/link Email Feedback|
|Author:||Stiefel, Chana Freiman|
|Article Type:||Cover Story|
|Date:||May 2, 1997|
|Previous Article:||1918 flu found.|
|Next Article:||Give me an 'A.' July 4th displays get an explosive new look: fireworks you can read.|