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2017考研英语阅读理解冲刺模拟试题及答案(21)
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 countrywomen 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 Guanglun 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, development 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...