首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Dolly was once an awfully lonely sheep. When the famous cloned (of an exact copy of a plant or animal made by taking a cell from
Dolly was once an awfully lonely sheep. When the famous cloned (of an exact copy of a plant or animal made by taking a cell from
admin
2009-03-21
63
问题
Dolly was once an awfully lonely sheep. When the famous cloned (of an exact copy of a plant or animal made by taking a cell from it and developing it artificially) animal made headlinesin 1997, she was the only mammal ever to be manufactured from the cell of an adult donor. Since then, the clone ranks have swelled, with mice and cattle also making their way out of the labs. Last week cloning technology took another step forward when an international biotechnology company announced that it had created a litter of five genetically identical piglets (young pigs), and that it had a pretty good idea of how they could one day be used as organ donors for ailing humans.
The idea of turning pigs into
tissue factories
has been around for at least 30 years. Pigs breed easily and mature quickly, and their organs are roughly the same size.as those of humans, meaning operations can be performed with a relative snap-out, snap-in simplicity. The problem is, once the donor organ is stitched in place, the body rebels, rejecting it even more violently than it would a human transplant. " A pig heart transplanted in a person would turn black within minutes, " says David Ayares, a research director with PPL Therapeutics, the biotech firm that helped clone Dolly and also produced the piglets.
What causes pig organs to be rejected so quickly is a sugar molecule on the surface of pig cells that identifies the tissue as unmistakably nonhuman. When the immune system spots this marker, it calls out its defenses. PPL scientists recently succeeded in finding the gene responsible for the sugar and knocking it out of the nucleus of a pig cell. Their next step would be to extract that nucleus, insert it into a pig ovum, and then into the womb of a host pig. The sugar free piglet that was eventually born could then be cloned over and over as a source of safe transplant organs. The idea is to arrive at the ideal animal and repeatedly copy it exactly as it is. The cloned piglets PPL introduced to the world last week were created in just this way, though for this first experiment in pig replication the scientists left the sugar genes intact.
Despite this recent success, PPL is not likely to be setting up its organ shop anytime soon. Knocking out the key sugar gene solves only the problem of short-term rejection. Much more has to be done before any solution to long-term rejection can be found. Nonetheless, Ayares is optimistic, insisting that pig organs could be available in as little as five years. For the present, even a little new transplant material is a big improvement over what’s available, and for gravely ill patients awaiting a donor, that’s no small thing.
What is true about Dolly according to the text?
选项
A、She was a lonely sheep in the first place.
B、She was manufactured out of the lab.
C、She was cloned from the cell of a mature sheep.
D、She was replaced by cloned piglets in terms of importance.
答案
C
解析
根据第一段首句“Dolly was once all awfully lonely sheep.”可知,多利曾经是一只孤单的绵羊,A选项中的“in the first place”意为“起初,首先”,与文意不符;根据该段第二句“…she was the only mammal ever to be manufactured from the cell of an adult donor”,可知,多利是唯一一只由原体提取的细胞培养而成的哺乳动物,并不是完全依靠实验室制造出来的,故B选项错误;adult donor与mature sleep意思相同,故C选项为正确答案;此处的adult donor即指代c中所说mature sheep;根据文章最后一句话“For the present,even a little new transplant material is a big improvement over what’s available…”可知,即使是一个细微的新的移植物在已有的技术基础上都将是一个重大的进步,全文并没有将克隆猪与克隆羊的重要性进行比较,故D选项错误。
转载请注明原文地址:https://kaotiyun.com/show/68Pd777K
本试题收录于:
公共英语四级笔试题库公共英语(PETS)分类
0
公共英语四级笔试
公共英语(PETS)
相关试题推荐
TheissueofonlineprivacyintheInternetagefoundnewurgencyfollowingtheSept.11terroristattacks,sparkingdebateover
Inathree-monthperiodlastyear,twoBrooklyniteshadtobecutoutoftheirapartmentsandcarriedtohospitalonstretchers
"Themoregadgetsthereare,the【31】______thingsseemtoget."saidHonoreErvin,co-authorofTheEtiquetteGirls:ThingsYou
"Themoregadgetsthereare,the【31】______thingsseemtoget."saidHonoreErvin,co-authorofTheEtiquetteGirls:ThingsYou
"Themoregadgetsthereare,the【31】______thingsseemtoget."saidHonoreErvin,co-authorofTheEtiquetteGirls:ThingsYou
"Themoregadgetsthereare,the【31】______thingsseemtoget."saidHonoreErvin,co-authorofTheEtiquetteGirls:ThingsYou
Somemoderncitiesareusuallyfamousforpeoplewholiveaverylongtime.
Earthquakescanbedevastating【1】disasters.TheinfamousSanFranciscoearthquakeof1906causedover$200millionworthofdam
Sincethedawnofhumaningenuity,peoplehavedevisedevermorecunningtoolstocopewithworkthatisdangerous,boring,burd
A、Michigan.B、Ohio.C、Massachusetts.D、Washington.C
随机试题
A.黄连阿胶汤B.朱砂安神丸C.两者均是D.两者均非(1996年第115,116题)不寐,急躁易怒,日赤口苦,口渴喜饮,小思饮食,溲干便黄,脉弦数者,应选用()
女,30岁。在颈丛麻醉下施行了甲状腺腺瘤切除术,手术顺利。该病人返回病房后应采用的卧位是
以下关于苦参的描述,错误的是()。
根据有关法律规定,招标代理服务收费方式是()
乌尔泰投资股份有限公司(以下简称“乌尔泰公司”)持有哈尔克公司60%的股权,能够对哈尔克公司实施控制。2×21年7月6日乌尔泰公司对哈尔克公司的长期股权投资的账面价值为6000万元,当日未存有计提的长期股权投资减值准备,乌尔泰公司将其持有的对哈尔克公司长
班级管理的本质在于()。
艺术通过它的艺术质料反映现实的真实,是一种多棱镜。绘画、音乐、雕塑、语言艺术的目的就是反映人类经验的真实,把确实从经验中感受到的东西表达出来,真确地传达出来,是一种长久的,几乎是无穷无尽的努力。它通过高水平的读者的鉴赏来检验,通过艺术批评家来总结规律和发现
德国人卡尔.奔驰研制的第一台以汽油为动力的汽车于1886年获得专利,从此汽油汽车______,燃烧汽油作为动力也似乎成为________的事,然而世界经济论坛评出的“2008年科技先驱”,却赫然将细菌“开动”小汽车列人其中。我们是否正在_______汽油汽
下列行为中,属于单方行为的是()
为考生文件夹下SCREEN文件夹中的PENCEL.BAT文件建立名为BAT的快捷方式,存放在考生文件夹下。
最新回复
(
0
)