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
61
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.
Compared with genetic engineering of food crops, genetic engineering of trees _____.
选项
A、began much later
B、has developed more slowly
C、is less useful
D、is less controversial
答案
B
解析
事实细节题。由题干中的genetic engineering of trees可定位到第一段最后一句。本文并没有提到树木基因改良技术从什么时候开始,所以有可能树木的基因改良技术和别的基因改良技术在开始的时间上相差不大,但在所取得的成果方面却有很大的差别,因此,本题关键在于理解第一段最后一句中的lag behind指的是程度上的落后,而非时间上的落后,故B项正确。
转载请注明原文地址:https://jikaoti.com/ti/GoFRFFFM
0
考研英语一
相关试题推荐
Thedifferencesinlivingstandardsaroundtheworldarevast.In1993,theaverageAmericanhadanincomeofabout$25,000.In
Researchersarefindingthatboysandgirlsreallyarefromtwodifferentplanets.Boysandgirlshavedifferent"crisispoints"
Shoppinghasalwaysbeensomethingofanimpulsiveactivity,inwhichobjectsthatcatchourfancywhilestrollingareimmediate
Theclassicdifficultyfeltwithdemocracyarisesfromthefactthatdemocracycanneverexpressthewillofthewholepeoplebe
Inthelate1960’s,manypeopleinNorthAmericaturnedtheirattentiontoenvironmentalproblems,andnewsteel-and-glassskysc
ReadthefollowingChinesetextandwriteanEnglishabstractof80-100words.YoushouldwriteyourabstractonANSWERSHEET2.
Thequestioningoftheroleofthepublicgalleryisnotanewphenomenon.Itissomethingthathasbeenarguedoversinceitsv
ResearchersledbyNewYorkUniversityneuroscientistJosephLeDouxrecentlyclaimedtobethefirstscientiststoeraseasingl
ResearchersledbyNewYorkUniversityneuroscientistJosephLeDouxrecentlyclaimedtobethefirstscientiststoeraseasingl
随机试题
Whatisyourfavoritecolor?Doyoulikeyellow,orange,red?【T1】Ifyoudo,youmustbeanoptimist,aleader,anactiveperson
当超声波从一个介质传播到另一个弹性、密度都不同于前者的介质时,声束方向将发生变化,该变化称为
由支原体引起的疾病是()。
2000年6月,最高法院决定定期向社会公布部分裁判文书,在汇编前言中指出:“最高人民法院的裁判文书,由于具有最高的司法效力,因而对各级人民法院的审判工作具有重要的指导作用,同时还可以为法律、法规的制定和修改提供参考,也是法律专家和学者开展法律教学和研究的宝
连锁经营最基本、最明显、最本质的特征()。
信用社办理支付结算,因工作差错发生延误,影响客户和他行资金使用的按中国人民银行规定的同档次()。
从业者步入职业殿堂的“通行证”,体现着从业者的道德操守和人格力量,并且还是具体行业立足的基础的是()
(00年)假设某企业在两个相互分割的市场上出售同一种产品,两个市场的需求函数分别为p1=18-2Q1,p2=12-Q2其中P1和P2分别表示该产品在两个市场的价格(单位:万元/吨),Q1和Q2分别表示该产品在两个市场的销售量(即需求量,
Writeanessayof160~200wordsbasedonthefollowingdrawing.Inyouressayyoushould:1)describethedrawingbriefly,
Afterthebirthofmysecondchild,Igotajobatarestaurant.Havingworkedwithanexperienced【C1】______forafewdays,Iw
最新回复
(
0
)