四六级

　　英语四级阅读理解占总分的35%，相对来说比重较大，所以这部分对四级取得高分是关键，考生们需要多做题、多练习。小编为大家整理了英语四级阅读理解200篇精讲，希望可以帮助到大家。

英语四级阅读理解200篇：英科学家用基因编辑造“抗病猪”

　　不少人都听说过用转基因改造生物。多年来，科学家一直在研究修改生物和植物的DNA，以从某种方式上改变它们的特征。生活中最常见的例子就是转基因食品。现在，科学家可对猪的基因进行改造，从而提起它们的存活率。他们使用的技术不是转基因，而是基因编辑。区别是什么呢？跟随本期选文寻找答案。

　　Vocabulary: Genetics and disease 词汇: 遗传学和疾病

　　By now, most of us will have heard of GMOs. In case you haven't, GMO stands for genetically-modified organism. This basically means that an organism has had a foreign genetic sequence introduced into it. In theory, this gives the organism certain advantages – it may become hardier by developing a resistance to disease, or in the case of GM food, may be bigger and require fewer nutrients to develop.

　　GM organisms have been used for a while. Scientists in the UK are trialling a GM wheat which allegedly yields40% more crop in greenhouse conditions. GM hens, which are able to lay eggs from different poultry breeds, have been used by scientists in Edinburgh to conserve rare birds by storing their stem cells in a seed bank. And more recently, scientists in China used information from the genome of a plant to increase the production of a key malaria drug, helping to meet the large global demand.

　　But now scientists at the University of Edinburgh's Roslin Institute have created GE pigs which are allegedly immune to one of the world's costliest livestock diseases. GE stands for gene editing. Unlike GM, gene editing merely alters the DNA of the creature. In this case, a small region of pig DNA was deleted, preventing contraction of the PRRS virus, or Porcine Reproductive and Respiratory Syndrome virus.

　　The virus causes breathing problems and death, but even after the GE pigs were exposed to it, none have become ill. And the effect is permanent, so the resistance will be passed on through natural breeding. Tests so far showed that the animals are not weakened in any other way by the process, claims Research leader Dr Christine Tait-Burkard. "The main thing that this edit will do is benefit animal welfare because the animals will not get a devastating disease."

　　However, critics have argued that the creature's welfare will actually suffer because of this. Helen Browning of the Soil Association believes this only addresses the symptom of the problem and not the root cause. "It is not encouraging companies to change the way they keep their pigs so they don't become diseased in the first place", she says.

　　Regardless, this is an experiment and while the technique appears to work, it is several years away from regulation and implementation. “On top of that, only if these studies are successful and the public are accepting, would we integrate these gene edits into commercial breeding stocks," Dr Tait-Burkard told the BBC.  So it seems we may have a while yet.

　　词汇表

　　genetically-modified 转基因的

　　organism 生物体

　　genetic sequence 基因序列

　　hardy 强壮的

　　resistance to disease 抗病

　　nutrient 营养物，养分

　　trial 试验

　　stem cell 干细胞

　　genome 染色体组，基因组

　　drug 药物

　　immune 有免疫力的

　　DNA 脱氧核糖核酸

　　contract a virus 感染一种病毒

　　reproductive 繁殖

　　respiratory 呼吸的

　　syndrome 综合症

　　expose to (a virus) 感染（一种病毒）

　　pass on 传下去，遗传给...

　　symptom 症状

　　测试与练习

　　1. 阅读课文并回答问题。

　　1. What is a GMO?

　　2. True or false: Genetic modification and gene editing are the same thing.

　　3. What effect has gene-editing had on these pigs?

　　4. In what way does Helen Browning believe that gene editing targets the symptom and not the root cause of the problem?

　　5. Which word in the text means 'physical and mental health and happiness'?

　　2. 请在不参考课文的情况下完成下列练习。选择一个意思合适的单词填入句子的空格处。

　　1. I'm very ______. I almost never get sick and I've never broken a bone!

　　hardy       resistance       nutrient       immune

　　2. Anyone who has been to the tropics recently may have been ______ to the virus.

　　passed on       contracted       trialled       exposed

　　3. Whether or not your character is determined by your ______ is still hotly debated.

　　stem cell       DNA       syndrome       genetically-modified

　　4. The plants absorb water and other ______ through their roots.

　　resistances       nutrients       drugged       symptoms

　　5. The life-saving medicine is still undergoing ______, but should be available shortly.

　　trials       exposure       immunity       resistance

　　参考答案

　　1. 阅读课文并回答问题。

　　1. What is a GMO?

　　A GMO is a genetically-modified organism.

　　2. True or false: Genetic modification and gene editing are the same thing.

　　False. Genetic modification introduces foreign material into a creature. Gene editing alters a creature's DNA.

　　3. What effect has gene-editing had on these pigs?

　　The pigs are allegedly immune to the PRRS virus.

　　4.In what way does Helen Browning believe that gene editing targets the symptom and not the root cause of the problem?

　　She says it doesn't encourage companies to improve the way they keep their pigs, stopping them from becoming diseased in the first place.

　　5. Which word in the text means 'physical and mental health and happiness'?

　　Welfare. (Critics have argued that the creature's welfare will actually suffer because of this.)

　　2. 请在不参考课文的情况下完成下列练习。选择一个意思合适的单词填入句子的空格处。

　　1. I'm very hardy. I almost never get sick and I've never broken a bone.

　　2. Anyone who has been to the tropics recently may have been exposed to the virus.

　　3. Whether or not your character is determined by your DNA is still hotly debated.

　　4. The plants absorb water and other nutrients through their roots.

　　5. The life-saving medicine is still undergoing trials, but should be available shortly.

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