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雅思阅读练习:Transplanting pig's organs into human?

2017-05-23 17:59:41来源:网络 柯林斯词典

  新东方在线雅思网为大家带来了雅思阅读练习:Transplanting pig's organs into human?。正文都做了贴心的注解,文章包含雅思词汇、例句讲解。希望以下内容能够为同学们的雅思备考提供帮助。新东方在线雅思网将第一时间为大家发布最新、最全、最专业的雅思报名官网消息和雅思考试真题及解析,供大家参考。

  这篇雅思阅读素材是要跟大家分享关于器官移植的话题。器官移植可以延长人类寿命,然而目前可用的器官却越来越难得到。科学家们认为,猪的器官可以移植到人类,但随之而来的是细胞病毒问题。而这个问题,现在似乎正在得到解决。或许在不远的将来,人类有望解决移植中器官供应不足的问题了。一起看看文章怎么说的吧!

  Transplanting(移植)organs brings life to the dying. But most donor organs are harvested from the dead. Shortfalls in the number of volunteer donors, the difficulty of gaining the consent of grieving relatives, and a reduction in most countries of the rate of fatal road accidents (the most reliable source of healthy organs), mean that there is a constant lack of them. Thousands die each year while on waiting lists for transplants. Researchers have, therefore, long sought ways to boost supply.

  One idea is to harvest animal organs. That is less mad than it sounds. A liver, a kidney(肾脏) or a cornea(眼角膜) does the same job, regardless of species(物种). And it works. In 1984 an American child lived for three weeks after receiving a baboon(狒狒) heart intended as a stopgap(临时替代) until a human donor could be found (unfortunately, one was not found in time). Conversely(相反的), human organs have been transplanted into animals for the purpose of research. Earlier this year, for example, a paper in the American Journal of Transplantation described moving kidneys from human fetuses(胎儿) into rats.

  Until now, though, two technical problems have stood in the way of (妨碍)routinely transplanting animal organs into people. One is that the recipient’s immune system (免疫系统)must be persuaded to tolerate a big chunk of (一大块)foreign tissue(人或动植物身体的组织). The other is that swapping(交换) tissues between species risks swapping diseases, too. This second problem may soon be addressed(解决), if George Church of the Harvard Medical School has his way. For, as he and his colleagues describe this week in Science, genetic engineering can now be used to eliminate(消灭)one of the most worrying types of pathogen (病菌)that might be spread via transplants.

  The animal most commonly suggested as a donor is the pig. Pigs are roughly the size of human beings. They are reasonably well understood. And millennia (几千年)of experience mean they are easy to breed. But they are not perfect. In particular, their DNA is full of retroviruses(反转录病毒,一种致肿瘤病毒), known specifically as porcine endogenous retroviruses(内源性反转录病毒), or PERVS. The genes of these viruses hitch a lift(搭顺风车) from one pig generation to another as an integral part of the porcine genome, whence they can break out and cause infection. And tests in laboratories suggest that, given the opportunity, they can infect human cells as well. (尤其是,猪的DNA中携带大量反转录病毒,确切些是猪的内源性反转录病毒(PERVS)。携带这些病毒的基因随着遗传基因组在猪群中代代相传,在传递过程中就会引起感染。实验研究表明,只要给机会,这些病毒也可感染人体细胞。)

  The existence of PERVs, then, has been one of the main obstacles to transplanting pig organs into people.

  Dr Church and his colleagues thought PERVs ideal candidates to test the mettle(勇气;气概)of one of the rising stars of biotechnology(生物技术), CRISPR/Cas9. This is a gene-editing technique derived from bacteria, which use it as a sort of immune system. In nature, it recognises specific sequences of viral DNA and chops the DNA molecule (分子) apart at these points, protecting the bacterium from harm. Tweaked (稍微调整)a bit in the laboratory, it can be made to recognise any DNA sequence and do likewise. This permits specific stretches of DNA to be deleted(删除) from genomes, and also allows new stretches to be inserted into the gap thus created. (CRISPR/Cas9能识别携带病毒的DNA序列,在感染病毒的地方将DNA分子与病毒DNA分开以防止病毒的侵害。通过实验稍做调整后,CRISPR/Cas9就能用于识别各种DNA序列,将特定的DNA序列从基因组中删除,并把新的DNA序列植入由此带来的空缺中。)

  Dr Church and his fellow researchers analysed the genetic sequences of one family of PERVs,with a view to (旨在)attacking them with CRISPR/Cas9. They found that the sequence of the gene which lets the virus integrate itself into its host’s DNA is the same from one strain of virus to another. That allowed them to program a CRISPR/Cas9 system to look for this particular sequence and chop it out of the genome. (丘奇博士和他的同事们研究了一种PERVS基因序列,旨在用CRISPR/Cas9来攻击这些序列。他们发现,能让PERVS与主体的DNA结合的基因序列与使一类病毒与主体的DNA结合的基因序列是一样的。所以他们能够设计出一类CRISPR/Cas9 来识别这个特定的病毒基因序列并把它从基因组中去掉。)

  The porcine kidney cells Dr Church used for his experiments had 62 PERVs embedded (嵌入,植入)in their genomes. He and his colleagues tested their molecular scissors on several lines of these cells. In the most responsive, they managed to snip out (剪掉)all 62 copies of the integration gene.

  Since PERVs rely on this gene to infect human cells as well as porcine ones, deleting it should stop them jumping into human hosts. Sure enough, tests in Petri dishes (皮氏培养皿)showed that the modified pig cells did not infect human cells grown alongside them. And, despite the extensive edits made to their DNA, those pig cells seemed unharmed by the procedure.

  The editing would need to be done to sex cells, or their precursors(先导细胞), if actual lines of “clean” pigs were to be bred for use as organ donors. But this is still a striking result. Not only does it demonstrate that it is possible to cleanse(清洗) animal cells of unwanted viral passengers, thus helping remove one of the big barriers to cross-species organ transplants; it also shows the power of a genetic-engineering technique that has existed for only three years. (它不仅展示了我们可以将不需要的病毒过客从动物细胞中清洗出去,从而有助于解决跨物种器官移植的大障碍;还展示了存在仅仅三年的基因工程技术的力量所在。)

  Vocabulary

  transplant 移植

  kidney 肾

  species 物种

  stopgap 临时替代物

  conversely 相反地

  fetus 胎儿

  immune system 免疫系统

  tissue 组织

  swap 交换

  address 解决(问题)

  eliminate 消灭

  millennium 千年

  molecule 分子

  delete 删除

  with a view to... 旨在做......

  embed 嵌入

  cleanse 清洗

  Transplant引起的词汇

  Transplant 移植

  Transfer 转移;调动

  Transparent 透明的

  Transfuse 输血

  Transport 运输

  Transmit 传递,传播

  transcribe 抄写;誊写

  transient 短暂的;过渡的

  transcend 超越;跨越

  transgress 越过;违反


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