每天推送一条四六级听力考试真题的音频。希望对大家的四六级考试有所帮助。 　　1. 　　A. High-fiber wheat. 　　B. Mushrooms that keep their color. 　　C. Highly-productive tomatoes. 　　D. Rice that resists pollution. 　　2. 　　A. Genetically modified. 　　B. Genetically edited. 　　C. Graft. 　　D. Genic mutation. 　　1. According to the news report, which of the following crops has not been developed yet based on gene editing 　　A. High-fiber wheat. 　　B. Mushrooms that keep their color. 　　C. Highly-productive tomatoes. 　　D. Rice that resists pollution. 　　2. According to the news report, what technology is it when it comes to adding DNA from another organism 　　A. Genetically modified. 　　B. Genetically edited. 　　C. Graft. 　　D. Genic mutation. 　　Foods based on the latest biotechnologies（生物技术） will soon be available in grocery stores（杂货商店） around the country. The first foods from plants or animals that have had their genetic material, or DNA, "edited" are expected to appear on the market as early as next year. Genetically edited food uses a different technology from "genetically modified," or GMO, foods（转基因食物）, which are already available in many countries including the U.S. Gene editing is needed to improve food production in order to feed the world's growing population. However, governments do not yet know how to oversee（监视，监督） this new tool. It also is unclear whether people will be willing to buy gene-edited foods. Researchers are using the technology to make several new kinds of crops. They include high-fiber（高纤维的） wheat, mushrooms that keep their color and highly-productive（高产的） tomatoes. They also are trying to develop corn that resists（抵抗） dry weather conditions and rice that resists pollution. For hundreds of years, farmers have genetically changed crops and animals by breeding（培育） them for desired qualities. This selective（选择性的） breeding results in giving up some other qualities. GMOs, or genetically modified organisms, are plants and animals that have had DNA from other kinds of organisms mixed with their own to give the new organism a specific quality. Scientists around the world say GMOs are safe to eat. But that does not keep some people from not liking them. Some people also worry that GMOs will bring unexpected results as they interact with other living things in the natural world. Now there are gene-editing tools. Scientists hope these methods will permit very exact changes to plant or animal DNA without necessarily adding DNA from another organism. So far, researchers have placed most of their efforts not on adding to DNA but on cutting unwanted parts from genes causing them to "turn off." 　　背景知识： 　　转基因技术的理论基础来源于进化论衍生来的分子生物学。基因片段 [2] 的来源可以是提取特定生物体基因组中所需要的目的基因，也可以是人工合成指定序列的DNA片段。DNA片段被转入特定生物中，与其本身的基因组进行重组，再从重组体中进行数代的人工选育，从而获得具有稳定表现特定的遗传性状的个体。该技术可以使重组生物增加人们所期望的新性状，培育出新品种。 　　基因编辑技术指能够让人类对目标基因进行“编辑”，实现对特定DNA片段的敲除、加入等。而CRISPR/Cas9技术自问世以来，就有着其它基因编辑技术无可比拟的优势，技术不断改进后，更被认为能够在活细胞中最有效、最便捷地“编辑”任何基因。