Voice of America, April 11, 2003

New research suggests human cloning is extremely difficult and may be impossible.

U.S. scientists say they have found that cells from humans and other primates, such as apes, divide in a different manner than cells of other animals, so the laboratory processes necessary to make a clone, an exact genetic duplicate, of a higher animal are extremely difficult.

Researchers from the University of Pittsburgh say this explains why hundreds of attempts to clone monkeys have been unsuccessful. Humans,like monkeys, are primates. Dozens of animal clones including cows, pigs, sheep and a cat, have been born since 1997, but many such experiments have produced still-born animals, or clones with serious defects.

Animal cloning procedures call for the removal of all DNA material, including chromosomes, from a host cell, then replacing the cell's nucleus with genetic material from the animal being cloned. Scientists trying to perform this procedure on primate cells say proteins needed to ensure correct cell division are lost when DNA is removed, so chromosomes from the "parent" cell are not duplicated correctly. All such experiments have failed.

Gerald Schatten of the University of Pittsburgh medical school, is quoted as saying his research team's discoveries cast further doubt on recent claims of successful human cloning experiments by members of the Raelians, a religious sect based in Canada. Mr. Schatten says only "unethical charlatans" could contend that human cloning is a practical procedure at the present time.