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  3. Many experts who favor genetically modified foods believe that genetic engineering can help to meet the demands of the world’s i

Many experts who favor genetically modified foods believe that genetic engineering can help to meet the demands of the world’s i

admin2009-04-23  52
问题 Many experts who favor genetically modified foods believe that genetic engineering can help to meet the demands of the world’s increasing population.
The plants would be insect resistant as a gene from the soil bacterium could direct cells to produce ______ that is toxic to certain insects.
选项
答案a crystalline protein
解析 农作物植入抗虫害基因可以对一些害虫产生“免疫”，这里面的作用机理在文章里有表述"To date, insect resistance has been provided by a gene from the soil bacterium Bacillus thuringiensis(Bt). This gene directs cells to manufacture a crystalline protein that is toxic to certain insects—especially caterpillars and beetles that gnaw on crops—but does not harm other organisms"——作物植入抗虫基因，也产生了优劣参半的后果。目前，抗虫害的特性是取自土壤中杆菌苏力菌(Bacillus thuringiensis,下文简称Bt)的—个基因。这个基因会促使细胞制造—种晶体状蛋白质，对某些昆虫来说是毒药，尤其是啃食作物的毛毛虫和甲虫，却不会伤害其他生物；而且不同的苏力菌菌株，各有不同的毒基因，影响的昆虫也不同。
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