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英语四级阅读理解精炼50篇025: 食用转基因食品安全吗(含答案)

hetao 于2014-06-12发布 l 已有人浏览
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英语四级阅读理解精炼第025篇,练习关于食用转基因食品安全吗的阅读理解,含有四级阅读练习题,参考译文,答案等内容。供正在准备英语四级考试的学习者参考学习。

cet4英语四级阅读理解精炼50篇

25. is gm food safe to eat ?

traditional plant breeding involves crossing varieties of the same species in ways they could cross naturally. for example, disease-resistant varieties of wheat have been crossed with high-yield wheat to combine these properties. this type of natural gene exchange is safe and fairly predictable .

genetic engineering ( ge) involves exchanging genes between unrelated species that cannot naturally exchange genes with each other. ge can involve the exchange of genes between vastly different species — e. g. putting scorpion toxin genes into maize or fish antifreeze genes into tomatoes. it is possible that a scorpion toxin gene , even when it is in maize dna1 , will still get the organism to produce scorpion toxin — but what other effects may it have in this alien environment? we are already seeing this problem — adding human growth hormone genes to pigs certainly makes them grow — but it also gives them arthritis and makes them cross-eyed , which was entirely unpredictable.

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