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  3. Genetic engineering holds great potential payoffs for farmers and consumers by making crops resistant to pests, diseases, and ev

Genetic engineering holds great potential payoffs for farmers and consumers by making crops resistant to pests, diseases, and ev

admin2009-05-21  138
问题     Genetic engineering holds great potential payoffs for farmers and consumers by making crops resistant to pests, diseases, and even chemicals used to kill surrounding weeds; but new research raises concerns that altering crops to withstand such threats may pose new risks--from none other than the weeds themselves. This is due to the weeds’ ability to acquire genes from the neighboring agricultural crops. Researchers found that when a weed cross-breeds with a farm-cultivated relative and thus acquires new genetic traits--possibly including artificial genes engineered to make the crop hardier--the hybrid weed can pass along those traits to future generations.
    "The result may be very hardy, hard-to-kill weeds," said Allison Snow, a plant ecologist at Ohio State University in Columbus who conducted the experiments over the past six years along with two colleagues. They presented their results last week at the annual meeting of the Ecological Society of America in Madison, Wisconsin.
    The findings suggest that genetic engineering done with the aim of improving crops--growing the new genetic traits such as resistance to herbicides or pests-- could ultimately have unintended and harmful consequences for the crops if weeds acquire the same trait and use it to out-compete the crops. "Gene movement from crops to their wild relatives is an ongoing process that can be ultimately harmful to crops," said Snow.
    The results of the experiments challenge a common belief that hybrids gradually die out over several generations, Snow explained. "There has been an assumption that crop genes wouldn’t persist in crop-weed hybrids" because hybrids are thought to be less successful at reproducing, she said. However, Snow’s research contradicted this assumption: Hybrid wild radishes survived in all six generations that were grown since the study began.
    Although the genetic traits the scientists monitored were natural and not genetically engineered, the findings nonetheless suggest that artificial improvements introduced into crops through genetic engineering could spread to weeds and become permanent traits of the weed population.
    So strengthened, the weeds may pose a serious risk to the long-term health of agricultural crops. The danger exists in a number of crop plants--including rice, sunflower, sorghum, squash, and carrots--that are closely related to weeds with which they compete. Snow is concerned that the transfer of genes from crops to related weeds could rapidly render many herbicides (chemicals which kill weeds) ineffectual. That situation, she said, would be much like bacterial diseases acquiring resistance to antibiotics.
    Because plant hybrids arise in a single generation, however, it could happen much more quickly; "Modern agriculture is heavily dependent on herbicides," she said, "so people will notice when those don’t work anymore."
选项 A、threats posed by chemicals used to kill weeds
B、risks of altering crops’ genetic make up’s
C、dangers inherent in the nature of weeds
D、the results of recent research
答案B
解析 这是一道词义题。题干中的信号词出自于文章第一段第二句话中。文章第一段指出：新的研究引发了人们的这些忧虑，改变农作物，以便它们抵御这样的灾害可能导致新的危险——不是别的，正是杂草本身；这是因为，杂草能够从邻近的农作物那里获得基因。这说明，该单词应该是指改变农作物成分的风险。B说“改变农作物的基因成分的风险”，这与文章的意思相符。与A和C有关的信息是第一段的第一句话，但并不是该词所指的内容；与D有关的信息是第一段的最后一句话，文中是说“研究人员发现，当一种杂草与农场栽培的农作物类植物杂交时它就因此获得新的基因特征”，这也不是该词所指的内容。
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