The researchers, led by Hwang Woo-suk, insist they cloned an Afghan hound, only to help investigate (研究) human disease, including the possibility of cloning stem cells (干细胞) for treatment purposes.
But others immediately renewed calls for a global ban (禁令)on human reproductive cloning before the technology moves any farther.
"Successful cloning of an increasing number of species confirms the general impression that it would be possible to clone any species of mammals, including humans," said Ian Wilmut, a reproductive biologist at the University of Edinburgh who produced the first cloned mammal, Dolly the sheep, from an adult cell nearly a decade ago.
Researchers have since cloned cats, goats, cows, mice, pigs, rabbits, horses, deer, mules and gaur, a large wild ox of Southeast Asia. So far, efforts to clone a monkey or another primate with the same techniques have failed.
Uncertainties about the health and life span (寿命) of cloned animals continue to exist; Dolly died at a young age in 2003 after developing cancer and arthritis.
Wilmut and others complimented Hwang's achievement, reported Wednesday in the journal Nature. But they said politicians and scientists must face the larger issue — how to go on with the research without crossing the moral boundary of copying human life in the lab.
"The ability to use the technology is hopeful," said Robert Schenken, president of the American Society for Reproductive Medicine. "However, the paper also points out that in dogs as in most species, cloning for reproductive purposes is unsafe."
The cloned puppy was the lone success from more than 100 dogs implanted (嵌入)with more than 1,000 cloned embryos.
In a news conference in Seoul, the cloning team also condemned(谴责)the reproductive cloning of humans as "unsafe and inefficient." Human reproductive cloning already is banned in South Korea. Other nations, including the United States, are divided on whether to ban just human cloning or cloning of all kinds, including the production of stem cells.
56. An Afghan hound is a kind of ______.
A. cat B. goat c. cow D. dog
57. A ______ is a large wild ox of Southeast Asia.
A. horse B. deer C. mules D. gaur
58. Accrding to the passage, scientists haven’t been able to clone a ______ so far.
A. deer B. mule C. mouse D. monkey
59. The underlined word complimented is probably similar in meaning to ______.
A. praised B. doubted C. refused D. gave up
60. The cloning of human beings is banned in ______.
A. South Korea B. the United States
C. both South Korea and the United States D. neither South Korea nor the United States
