Five cloned pigs，whose organs are much less likely to be rejected(排斥) by a patient，have been born in the U．S.
More than 62,000 people in the U．S. alone are waiting to ____ donated hearts，lungs and so on.The number of human donors falls far short of ____.Pig organs are of a(n) ____ size to human organs，and some scientists hope they might be used to help meet the ____.But previous attempts to transplant pig tissue into humans have ____.
The five pigs ____ a gene that adds a sugar to the surface of pig cells.The sugar would ____ immune(免疫的) rejection of the tissue.“This advance provides a neartime ____ for overcoming the problem that there is not enough human organs for transplants，”says an expert.“This is the ____ gene for overcoming the ____ stage of rejection.”
____，scientists warn that much more work is necessary ____ organs from copies of the pigs could be transplanted into humans.Human genes will need to be added，to ____ rejection of the organ in the long term.There are also ____ that pig viruses could infect patients.
Cloning techniques were ____ to the production of the pigs.Genes can only be knocked out(去除) in a single cell.Cloning of these single cells then allowed the ____ of a whole animal in which the gene was knocked out in every cell.But the PPL researchers have ____ in knocking out only one copy of the gene.The team will now attempt to knock out both copies of the gene.
The team will also ____ tests to investigate whether a virus from the pigs could infect human cells.“Although a lot of the work is very ____，we’re still very far off being able to grow an organ，” says Julia，who is working on this project and quite ____ to creating similar knockout pigs with researchers at the University of Missouri.
| 小题1: | | A．exchange | B．check | | C．possess | D．receive |
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| 小题2: | | A．discussion | B．demand | | C．doubt | D．distance |
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| 小题3: | | A．beneficial | B．identical | | C．similar | D．certain |
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| 小题4: | | A．shortage | B．condition | | C．satisfaction | D．argument |
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| 小题5: | | A．continued | B．failed | | C．finished | D．paused |
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| 小题6: | | A．lack | B．include | | C．make | D．change |
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| 小题7: | | A．leave | B．cause | | C．block | D．destroy |
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| 小题8: | | A．supply | B．ambition | | C．contribution | D．solution |
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| 小题10: | | A．last | B．whole | | C．next | D．early |
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| 小题11: | | A．However | B．Therefore | | C．Besides | D．Finally |
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| 小题12: | | A．because | B．before | | C．if | D．after |
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| 小题13: | | A．prevent | B．ignore | | C．judge | D．weaken |
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| 小题14: | | A．regrets | B．emotions | | C．concerns | D．interests |
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| 小题15: | | A．simple | B．vital | | C．unusual | D．basic |
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| 小题16: | | A．collection | B．application | | C．reception | D．creation |
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| 小题17: | | A．delighted | B．succeeded | | C．joined | D．believed |
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| 小题18: | | A．conduct | B．plan | | C．design | D．study |
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| 小题19: | | A．perfect | B．strange | | C．exciting | D．disappointing |
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| 小题20: | | A．opposed | B．used | | C．devoted | D．suited |
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