2007北京太奇培訓(xùn)學(xué)�？佳杏⒄Z強(qiáng)化班授課講義(十三)

I. Reading Comprehension:

Text  1

    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 – giving them 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 which 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 any more. ”  (441 words)

Notes: none other than 不是別的，正是…；cross-breed (with) 雜交；hardy a. 強(qiáng)壯的，耐寒的；pass along…to 把…傳給；hybrid 雜交的；herbicide 除草劑；reproduce 繁殖；radish小蘿卜；sorghum 高粱；squash南瓜。

1. The word “This” in Line 3, Para. 1, most probably refers to __________.

  A. the great results made in recent research              B. risks of altering crops’ genetic make-ups
  C. dangers inherent in the nature of weeds              D. threats posed by chemicals used to kill weeds

2. According to the text, genetic engineering can be used to ___________.

  A. kill the weeds in fields through cross-breeding        B. give crops new genetic traits and make them hardy
  C. improve the yield and quality of most crops          D. make crops resistant to many of chemical fertilizers

3. Genetically modified crops could have harmful effects since ___________.

  A. gene movement between cultivated plants and wild ones is inevitable
  B. genetically altered plants are in a position to develop into weeds
  C. it is generally accepted that cross-breeding is a natural process
  D. in general hybrids are more successful at breeding than natural plants

4. Allison Snow uses the example of wild radishes to argue that __________.

  A. most of hybrids are certain to vanish in the future generations
  B. hybrids are regarded as being less successful at reproducing
  C. hybrid wild radishes can be grown in artificial environment
  D. new genetic traits could continue to exist in crop-weed hybrids

5. From the text we can see that the author seems ___________.

  A. biased           B. impartial             C. worried             D. optimistic