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
考研
If you go down to the woods today, you may meet high-tech trees—genetically modified to speed their growth or improve the qualit
If you go down to the woods today, you may meet high-tech trees—genetically modified to speed their growth or improve the qualit
admin
2015-07-13
16
问题
If you go down to the woods today, you may meet high-tech trees—genetically modified to speed their growth or improve the quality of their wood. Genetically-engineered food crops have become increasingly common, albeit controversial, over the past ten years. But genetic engineering of trees has lagged behind.
Part of the reason is technical. Understanding, and then altering, the genes of a big pine tree are more complex than creating a better tomato. While tomatoes sprout happily, and rapidly, in the laboratory, growing a whole tree from a single, genetically altered cell in a test tube is a tricky process that takes years, not months. Moreover, little is known about tree genes. Some trees, such as pine trees, have a lot of DNA—roughly ten times as much as human. And, whereas the Human Genome Project is more than halfway through its task of isolating and sequencing the estimated 100,000 genes in human cells, similar efforts to analyze tree genes are still just saplings.
Given the large number of tree genes and the little that is known about them, tree engineers are starting with a search for genetic "markers". The first step is to isolate DNA from trees with desirable properties such as insect resistance. The next step is to find stretches of DNA that show the presence of a particular gene. Then, when you mate two trees with different desirable properties, it is simple to check which offspring contain them all by looking for the genetic markers. Henry Amerson, at North Carolina State University, is using genetic markers to breed fungal resistance into southern pines. Billions of these are grown across America for pulp and paper, and outbreaks of disease are expensive. But not all individual trees are susceptible. Dr. Amerson’s group has found markers that distinguish fungus-resistant stock from disease-prone trees. Using traditional breeding techniques, they are introducing the resistance genes into pines on test sites in America.
Using genetic markers speeds up old-fashioned breeding methods because you no longer have to wait for the tree to grow up to see if it has the desired traits. But it is more a sophisticated form of selective breeding. Now, however, interest in genetic tinkering is also gaining ground. To this end, Dr. Amerson and his colleagues are taking part in the Pine Gene Discovery Project, an initiative to identify and sequence the 50,000-odd genes in the pine tree’s genome. Knowing which gene does what should make it easier to know what to alter.
It is discovered by Henry Amerson’s team that _____.
选项
A、southern pines cannot resist fungus
B、all southern pines are not susceptible
C、the genetic marker in southern pines was the easiest to identify
D、fungus-resistant genes came originally from outside the U.S.A
答案
B
解析
事实细节题。根据题干中的人名Henry Amerson可定位至第三段。B项是一个半否定的句式,因此本题关键在于理解B项的All…are not…结构在意义上等同于第三段倒数第三句的not all…are…。
转载请注明原文地址:https://kaotiyun.com/show/D074777K
0
考研英语一
相关试题推荐
Shoppinghasalwaysbeensomethingofanimpulsiveactivity,inwhichobjectsthatcatchourfancywhilestrollingareimmediate
Yourresearchteamhassurveyedstudentsinyouruniversityabouttheirattitudetowardsconsumption.Writeafindingreportwit
TheAfricans’interestistoguardpreferentialexportrulesenshrinedinthetemporaryAfricanGrowthandOpportunityAct,pass
Inthelate1960’s,manypeopleinNorthAmericaturnedtheirattentiontoenvironmentalproblems,andnewsteel-and-glassskysc
Amajorreasonforconflictintheanimalworldisterritory.Themaleanimal【C1】______anarea.Thesizeoftheareaissufficie
Amajorreasonforconflictintheanimalworldisterritory.Themaleanimal【C1】______anarea.Thesizeoftheareaissufficie
Nowmedicalresearchersarediscoveringatruism:"alcoholandtobaccodonotmix."Thesetwosubstances,bothdangeroustoheal
Becauseagricultureissoimportanttoanation’swell-being,governmentshavealwaysbeenconcernedwithit.Forexample,theU
Whenourchildrenareborn,westudytheireveryeyelashandmarvelattheperfectionoftheirtoes,andinnotimebecomeexper
Publicserviceannouncementsdonatedbyradio,print,televisionandInternetmediawillattempttoconvincekidsandtheirpare
随机试题
在考生文件夹下,“samp1.accdb”数据库文件中已建立两个表对象(名为“员工表”和“部门表”)和一个窗体对象(名为“fEmp”)。试按以下要求顺序,完成表及窗体的各种操作。建立“员工表”和“部门表”的表间关系,并实施参照完整。
政策方案的评估与择优主要有下列哪些方法?()
破坏性可靠性试验的试验准备中,传动轴应处于允许的()状态。
Healwaysdidwellatschooleverynowandthen.______(尽管得做兼职)everynowandthen.
下列哪一项不是人参的功效
金融工具的票面收益与该金额工具购买时市价的比率称为()。
下列各项因素中,不影响存货经济订货批量的有()。
中国结象征________、________、________的人际关系,主要有________和________两类。
2015年全国海洋生产总值64669亿元,比上年增长7.0%,海洋生产总值占国内生产总值的9.6%。其中,海洋第一产业增加值3292亿元,第二产业增加值27492亿元,第三产业增加值33885亿元。2014年,海洋工程建筑业增加值约是海洋盐业增加值的
问卷调查法的类型不包括()
最新回复
(
0
)