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  3. The Cell Nucleus Ports a Long Technique with Gram Depending on whom you ask, the experiment announced at a Texas medical con

The Cell Nucleus Ports a Long Technique with Gram Depending on whom you ask, the experiment announced at a Texas medical con

admin2013-05-04  58
问题              The Cell Nucleus Ports a Long Technique with Gram
    Depending on whom you ask, the experiment announced at a Texas medical conference last week was a potential breakthrough for infertile women, a tragic failure or a dangerous step closer to the nightmare scenario of human cloning.
    There’s truth to all these points of view. Infertility was clearly the motivation when Chinese doctors used a new technique to help one of their country women get pregnant. Unlike some infertile women, the 30-year-old patient produced eggs just fine, and those eggs could be fertilized by sperm. But they never developed properly, largely because of defects in parts of the egg outside the fertilized nucleus. So using a technique developed by Dr. James Grifo at New York University, Dr. Zhuang Guangtun of Sun Yat-sen University in Guangzhou took the patient’s fertilized egg, scooped out the chromosome-bearing nuclear material and put it in a donated egg whose nucleus had been removed. In this more benign environment, deve-lopment proceeded normally, and the woman became pregnant with triplets who carried a mix of her DNA and her husband’s—pretty much like any normal baby.
    What has some doctors and ethicists upset is that this so-called nuclear-transfer technique has also been used to produce clones, starting with Dolly the sheep. The only significant difference is that with cloning, the inserted nucleus comes from a single, usually adult, cell, and the resulting offspring is genetically identical to the parent. Doing that with humans is ethically repugnant to many. Besides, for reasons that aren’t yet well understood, cloned animals often abort spontaneously or are born with defects; Dolly died very young, though she had seemed healthy. And because the Chinese woman’s twins were born prematurely and died (the third triplet was removed early on to improve chances for the remaining two), critics have suggested that cloning and nuclear transfer are equally risky for humans.
    Not likely, says Grifo. "The obstetric outcome was a disaster," he admits, "but the embryos were chromosomally normal. We have no evidence that it had anything to do with the procedure." Even so, concern over potential risks is why the Food and Drug Administration created a stringent approval process for such research in 2001—a process that Grifo found so onerous that he stopped working on the technique and gave it to the researchers in China, where it was subsequently banned (but only this month, long after Zhuang’s patient became pregnant) .
    The bottom line, say critics, is that perfecting a technique that could be used for human cloning, even if it were developed for another purpose, is just a bad idea—an assertion Zhuang rejects. " I agree that it makes sense to control these experiments," he says. "But we’ve developed an effective technology to help people. We understand how to do it. We need it."
The only difference existing between nuclear-transfer and cloning technique is______.
选项 A、whether it is used for research or for helping the infertile
B、whether the offspring looks like the parent
C、whether it is used in animals or human beings
D、whether the inserted nucleus comes from a single and usually adult cell
答案D
解析 事实细节题。原文对应信息在第三段第二句：“The only significant difference is that with cloning，the inserted nucleus comes from a single，usually adult，cell，and the resulting offspring is genetically identical to the parent．”
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