英文教材第十二章
第十二章动词不定式(思维导图+知识梳理+好题精炼)2022-2023初中英语中考语法归纳
第十二章动词不定式思维导图知识梳理一、不定式概述动词不定式的基本形式是:“t o+动词原形”,有时可以不带to.不带to的不定式与动词原形同形,但它不是原形,而是一种语法形式.除基本助动词do和情态动词外,英语动词都有不定式形式.动词不定式没有人称和数的变化,在句子中不能作谓语,但可以担任除谓语外的任何成分－主语、表语、宾语、定语、状语和宾语补足语.动词不定式和它的宾语或状语构成不定式短语.不定式有时态、语态变化(以do为例):动词不定式的句法作用(一)作主语用作主语的动词不定式通常表示一种具体的、特定的行为,其谓语动词用第三人称单数形式.To obey the laws is everyone's duty.服从法律是每个人的职责.How to use the computer is a question.怎么使用计算机是一个问题.How to get there is not decided yet.怎样去那里还没决定下来.点拨(1)在很多情况下,常用it作形式主语,而把真实主语不定式放在谓语之后.It was difficult to sell my car.我的车很难卖掉.It's not known where to stay for the night.在哪里过夜还不知道.(2)如果要表示不定式的动作是谁做的,一般在不定式前加一个for短语.It will be a regret for us not to help him.我们没有帮助他是个遗憾.(3)在某些形容词(如kind, good, nice, wise, unwise, clever, silly, wrong, right, foolish, stupid, careless, considerate, rude, naughty, impolite等)作表语时,不定式前常可加一个以of引起的短语,来说明不定式指的是谁的情况.It would be rude of us to refuse their invitation.(我们)拒绝他们的邀请,会显得无礼.(二)作表语作表语,一般紧跟在系动词,如:be, seem, get等后面,用以说明主语.The question is when to start.问题是什么时候启程.You seem to have lost weight.你好像减肥了.What we have to do first is to find a solution.我们得做的第一件事是找出一个解决办法.点拨当不定式所作的表语仅用来说明主语的内容时,这个不定式只作单纯的表语,而不具有未来的含义.(三)作宾语能以不定式作宾语的动词很多,常见的有:agree, begin, decide, expect, forget, hope, learn, like, manage, pretend, start, try, want, wish等.Do you wish to see the manager?你想见经理吗?They decided to learn English hard.他们决定好好学英语.Don't forget to meet me at 6:00.别忘了六点钟和我见面.有些动词,如:tell, advise, show, teach, know, forget, learn , remember, show,understand, see, wonder, hear, find out, explain, decide, discuss等后面,常用带疑问词的不定式作宾语.We don't know who(whom)to ask.我们不知道问谁.We asked how to get to the station.我们问怎么到达车站.Have you decided where to go for your holidays?你们决定到哪儿度假了吗?I don't know whether to apply for the job or not?那份工作我不知道申请还是不申请?(四)作定语I have no time to waste.我没有时间可浪费.Let me find a place to park.我来找个停车的地方.He is always the first to come to work and the last to leave.他总是第一个来上班,最后一个走.点拨不定式修饰something, anything, nothing时,放在它们的后面.如果something, anything, nothing 有形容词来修饰,词序是something(nothing...)+形容词＋不定式.My father had something to do.我父亲有事要办.Have you got anything important to buy?你有什么重要的东西要买吗?(五)作状语不定式常可用作状语,修饰动词,表示行为的目的、结果、原因等.一般放在被修饰词之后,但在表示目的时,为了强调也可放在句首.1.作目的状语为加强语气在否定式前还可加上in order或so as组成词组(即:in order to...,so as to...),作状语表示目的.To live a long and healthy life, we must learn to have a balanced diet.为了能过长寿而健康的生活,我们必须懂得吃均衡的食品.I stayed there so as to see what would happen.我留在那儿,为的是想看看会发生什么事.In order to help him, we would do everything we can.为了帮助他,我们愿意尽一切力量.2.作结果状语表结果,其逻辑主语通常亦是全句的主语.在“so...as to...”“such...as to..“enough to...”“only to...”以及“too...to...”等结构中的不定式皆表示结果.She is old enough to go to school.她已到了可以上学的年龄了.He was too drunk to drive home.他酩酊大醉,没法开车回家.3.作原因状语She trembled to think of the terrible accident.想到那可怕的车祸,她就不寒而栗.We jumped with joy to hear the news.听到这消息,我们都高兴地跳了起来.(六)宾语补足语1、有很多动词的后面都可以有不定式作宾语补足语常见的这类动词有:advise, ask, tell, help, wish, want, expect, forbid, persuade, press, request, teach, warn等.She asked her grandfather to play game with her.她请爷爷跟她一起做游戏.Mother told me to cook the meal.妈妈叫我做饭.2.有一些动词后用作宾语补足语的不定式通常不带to,这种动词有两类:一类是感觉动词,另一类是使役动词感觉动词:如feel, see, hear, watch, notice等.使役动词:如make, let, have等.Let me do it for you.让我来替你做.Don't let her go out.别让她出去.I made him work hard.我迫使他加劲干.(1)动词help之后,复合宾语中的不定式可带to,亦可不带to.在上述动词转换为被动结构时,其后的不定式必须带to.He was seen to enter the theatre.有人看见他走进了剧院.I was made to do my homework the whole night.我被迫整晚做作业.Can you help me (to) move this table?你能帮我移动一下这张桌子吗?(2)感官动词的宾语补足语有两种形式:不带to的不定式和动词-ing形式.I heard Meimei singing in her room when I went past.我路过的时候听见梅梅在房间里唱歌.(路过的瞬间正在唱,所以用singing)We often hear Meimei sing in her room.我们经常听见梅梅在房间里唱歌.(经常听见,用不定式)I saw him come in.I saw him coming in.两句话的意思都一样:我看见他进来.用不定式着重于动作的全过程,用动词-ing形式则是强调当时动作的进行情况.3.当谓语动词为think, make, find, consider, feel, regard等词,作宾语的不定式后面有宾语补足语时,常用it作形式宾语,而将真正的宾语放在补足语的后面I find it easy to learn English well.我发现要把英语学好很容易.三、不定式的主要句型及注意事项(一)不定式的否定式不定式的否定式:not+不定式,经常和ask(tell)sb. to do sth.句型连用.She asked me not to drive him to the station.她要我不要开车送他到车站.Try not to be late.争取不要迟到.Mary asked me not to give my pen to Jimmy.玛丽让我别把笔给吉米.She decided not to come here again.她决定不再到这儿来.点拨不定式的否定式和否定句的区别:I asked him not to open the door.我让他别把门打开.I didn't ask him to open the door.我没让他把门打开.(二)不定式的进行时态进行式:表示在谓语动词所表示的动作或状态发生时正在进行.It's nice to be sitting here with you.在这儿陪你坐着是非常愉快的.It is unwise for him to be talking that topic all the time.他老是谈论这件事,很不明智.(三)不定式的完成时态完成式表示在谓语动词的动作或状态发生时已经完成.She said she was sorry to have missed you.她说她没见到你很遗憾.He seemed to have visited our factory.他好像参观过我们的工厂.They appeared to have met before.他们看来以前见过面.(四)动词不定式的被动语态表示被动意义I didn't want to be told about it.我不想被告知这件事.Nothing seems to have been forgotten.似乎什么也没有被遗忘.The building is said to have been destroyed in a fire two years ago.据说这幢大楼两年前已毁于一场大火.在以某些形容词,如kind, good, silly, honest, bad, stupid, bold, clever, cruel,courteous, nice, rude, sensible, tactful, wise, wrong等作表语时,后面需用以“of+名词(或代词宾格)＋不定式”结构,以说明不定式所表示的动作的执行者是谁(即of短语是不定式的逻辑主语).It's very good of you to come.谢谢你的光临.How silly of you (it is)to make such a mistake!你出了这样的差错,多傻啊！It's very kind of you to say so.多谢你这么说.在had better, had best, would rather, would rather...than, would sooner, would sooner...than, cannot but, do nothing but等结构后面的不定式要省略“to”.You had better write it in English.你最好用英文写.I would rather stay at home.我宁愿待在家里.好题精练一、用-ing形式或不定式的适当形式完成句子1.Do you enjoy_________ football?(play)2.Fred didn't have any money, so he decided_________ a job.(take)3.We're going out for dinner, Would you like_________ us?(join)4.The teacher reminded the students_________ their test paper on time.(finish)5.When I was tired, I enjoyed_________ TV.(watch)6.It was a nice day, so the old man agreed_________ for a walk.(go)7.I'm not in a hurry, I don't mind_________.(wait)答案:1.playing2.to take3.to join4.to finish5.watching6.to go7.waiting二、选择括号内所给词组完成句子,注意括号内“go+v.-ing形式”构成固定搭配的用法(go boating; go fishing; go dancing; go running; go skating; go hunting; go singing)1.She's a good dancer. She always_________ on Saturday.2.I've got a gun. I'll_________ with that strong hunter next weekend.3.“Where is Tim?”“He has. _________ He always runs in the morning.”4.We have enough fish to eat. Our father_________ every day.答案:1.goes dancing2.go hunting3.gone running4.goes fishing三、仿照示例改写下列句子示例:It is very interesting to play baseball.→ To play baseball is very interesting.1.lt was not polite to speak that way before Mr. Lee.____________________________________________________________________________________________ 2.It can be quite easy to travel by air.____________________________________________________________________________________________ 3.lt will be no problem to arrive there before noon.____________________________________________________________________________________________4.To make those strangers believe us was so difficult.____________________________________________________________________________________________ 5.To help Tom speak Chinese well is not at all easy.____________________________________________________________________________________________ 答案:1.To speak that way before Mr. Lee was not polite.2.To travel by air can be quite easy.3.To arrive there before noon will be no problem.4.It was so difficult to make those strangers believe us.5.It is not at all easy to help Tom (to) speak Chinese well.四、选择填空1. _________ the bookstore, he stopped_________ a few books.A. Passing; buyingB. Passing; to buyC. To pass; buyingD. Having passed; to buy2.Bruce,look at your dirty shoes, You'd better_________ them right now.A. washedB. washingC. washD. to wash3. _________ the room, I found the computer_________.A. Entering; stealingB. Entering; stolenC. To enter; stealD. To enter; stealing4.We've worked hard for nearly one hour. Let's stop_________ a rest now.A. haveB. to haveC. havingD. have had5.My mother always tells me not_________ to the net bars(网吧)．A. goB. to goC. goesD. going6.The teacher asked us_________ English for half an hour in the morning.A. reads B reading C. to read D. read7.You will have to get up early tomorrow. Stop_________ TV, Peter.A. watchesB. watchC. to watchD. watching8.I find it hard_________ English well.A. learnB. learningC. to learnD. learns9.The teacher asked John_________ a short talk in our class meeting.A. giveB. to giveC. gaveD. giving10.The girl was too poor_________ a houseA. to buy; to live inB. to buy ;to liveC. buy; to liveD. buying; living in11.It was very late at night, but Mr. Brown still went on_________.A. works B .worked C. working D. work12.Remember_________ him about it before he goes away.A. tellB. to tellC. tellingD. to telling13.Lin Tao is strong enough_________ the big box.A. carryB. to carryC. carryingD. carries14.Her mother told her_________ in bed.A. not readB. not to readC. don't readD. to not read15.When class began, we stopped_________ to the teacher carefully.A. listeningB. listenC. listens D .to listen16.You'd better_________ the cinema by bus.A. don't goB. to goC. to go toD. go to17.What did the manager_________ you to_________ at the meeting?A. tell; sayB. ask; speakC. tell; speakD. ask; talk18.Tom was let_________ in the gate house.A. waitB. to waitC. waitingD. to have waited19.Mr.Hu has enough time_________ the job in two days.A. finishB. to finishC. finishingD. finished20.Look,the building_________ is our library.A. is repairedB. being repairedC. repairingD. to be repairing21. _________ no money, I could not buy this coat.A. HaveB. HavingC. To haveD. Have had22.The teacher has something important_________ us.A. to tellB. tellsC. tellingD. told23.Li Ming didn't know_________ next.A. to do whatB. what to doC. how to doD. what do24.I'd love_________ to your birthday party.A. comeB. cameC. to comeD. comes25.It took me two hours_________ by bus.A. to get thereB. to get to thereC. get thereD. get to there答案:1-5BCBBB 6-10CDCBA11-15CBBBD 16-20DABBB21-25 BABCA五、改正下列句子的错误1.He seems to not hear from her.____________________________________________________________________________________________ 2.I hope see you soon.____________________________________________________________________________________________ 3.I made them to give the money back.____________________________________________________________________________________________ 4.The scientist gave us some advice on how learning English.____________________________________________________________________________________________ 5.No one noticed him to leave the room.____________________________________________________________________________________________ 6.Have you given up to smoke?____________________________________________________________________________________________ 7.We found him waited at the school gate.____________________________________________________________________________________________ 8.Why not to turn off the light?____________________________________________________________________________________________ 9.She didn't want me go.____________________________________________________________________________________________ 10.I don't know to swim.____________________________________________________________________________________________ 11.China is a developed country belonging to the third world.____________________________________________________________________________________________ 12.It's getting dark. We have to find a hotel to live.____________________________________________________________________________________________ 13.He said he had an important meeting to attended.____________________________________________________________________________________________ 14.They don't allow that people smoke.____________________________________________________________________________________________ 15.It's difficult sell my car.____________________________________________________________________________________________ 答案:1.He seems not to...2.I hope to see...3.I made them give...4....how to learn...5....him leave...6....given up smoking?7...him waiting...8.Why not turn off...9.She didn't want me to go.10.I don't know how to swim.11....a developing...12....to live in13....to attend.14. ...people to smoke.15...to sell my car.。
《哈利波特与阿兹卡班囚徒》第12章《守护神》中英文对照学习版
中英文对照学习版Harry Potter and the Prisoner of Azkaban《哈利˙波特与阿兹卡班囚徒》Chapter TwelveThe Patronus第12章守护神Harry knew that Hermione had meant well, but that didn't stop him being angry with her. He had been the owner of the best broom in the worl d for a few short hours, and now, because of her interference, he didn't know whether he woul d ever see it again. He was positive that there was nothing wrong with the Firebolt now, but what sort of state would it be in once it had been subjected to all sorts of anti-jinx tests?哈利知道赫敏的用意是好的，但还是忍不住生她的气。
世界上最好的飞天扫帚，他拿到手里才短短几个小时，就因为赫敏横插一杠子，现在还不知道这辈子能不能再见到它。
哈利可以肯定火弩箭目前没有一点毛病，但是做了各种反恶咒的检测之后，会是什么模样，那就只有天知道了。
Ron was furious with Hermione, too. As far as he was concerned, the stripping-d own of a brand-new Firebolt was nothing l ess than criminal damage. Hermione, who remained convinced that she had acted for the best, started avoiding the common room. Harry and Ron supposed she had taken refuge in the library, and didn't try and persuad e her to come back. All in all, they were glad when the rest of the school returned shortly after New Year, and Gryffind or Tower became crowd ed and noisy again.罗恩也很生赫敏的气。
《哈利波特与魔法石》第12章《厄里斯魔镜》中英文对照学习版
中英文对照学习版Harry Potter and Philosopher’s Stone《哈利˙波特与魔法石》CHAPTER TwelveThe Mirror of Erised第十二章厄里斯魔镜Christmas was coming. One morning in mid-December Hogwarts woke to find itself covered in several feet of snow. The lake froze solid and the Weasl ey twins were punished for bewitching several snowballs so that they foll owed Quirrell around, bouncing off the back of his turban. The few owls that managed to battle their way through the stormy sky to deliver post had to be nursed back to health by Hagrid before they coul d fly off again.圣诞节即将来临。
十二月中旬的一天早晨，霍格沃茨学校从梦中醒来，发现四下里覆盖着好几尺厚的积雪，湖面结着硬邦邦的冰。
韦斯莱孪生兄弟受到了惩罚，因为他们给几只雪球施了魔法，让它们追着奇洛到处乱跑，最后砸在他的缠头巾后面。
几只猫头鹰飞过风雪交加的天空递送邮件，经历了千辛万苦，它们必须在海格的照料下恢复体力，才能继续起飞。
No one coul d wait for the holidays to start. While the Gryffind or common room and the Great Hall had roaring fires, the draughty corridors had become icy and a bitter wind rattled the wind ows in the classrooms. Worst of all were Professor Snape's classes d own in the dungeons, where their breath rose in a mist before them and they kept as cl ose as possibl e to their hot caul drons.大家都迫不及待地盼着放假。
anintroductiontogeneticanalysis(遗传学英文教科书第十二章)
Chapter 12Recombinant DNA Technology Key ConceptsRecombinant DNA is made by splicing a foreign DNA fragment into a small replicating molecule <such as a bacterial plasmid>, which will then amplify that fragment along with itself and result in a molecular clone of the inserted DNA.Restriction enzymes cut DNA at specific target sites, resulting in defined fragments with sticky ends suitable for insertion into a vector that has been cut open by the same enzyme.A collection of DNA clones that encompasses the entire genome of an organism is called a genomic library.An individual DNA clone can be selected from a library by using a specific probe for the DNA or its protein product or by its ability to transform a null mutant.DNA fragments of different sizes produced by restriction-enzyme digestion can be fractionated because they migrate to different positions on an electrophoretic gel.RNA or restriction-enzyme-cut DNA molecules that have been fractionated by size in an electrophoretic gel can be probed to detect a specific molecule.Restriction-enzyme target sites can be mapped, providing useful markers for DNA manipulation.A gene can be found by testing overlapping clones radiating outward from a linked marker. After a gene has been cloned, its nucleotide sequence can be determined, and the sequence can be used to study gene function and evolution.A pair of replication primers spanning a DNA sequence can be used to amplify that sequence for isolation.IntroductionThe goal of genetics is to study the structure and function of genes and genomes. Since Mendel's time, genes have been identified by observing standard phenotypic ratios in controlled crosses. Clues about gene function first came from correlating specific mutations with enzyme and other protein deficiencies. The correlation of mutant sites within a gene with amino acid substitutions in the appropriate protein led to a better understanding of gene structure and function. To these ideas were added discoveries about the nature of DNA and the genetic code, leading to a fairly comprehensive understanding of the basic nature of the gene. However, all were indirect inferences about genes; no gene had ever been isolated and its DNA sequence examined directly. Indeed, it seemed impossible to isolate an individual gene from the genome.Although it is relatively easy to isolate DNA from living tissue, DNA in a test tube looks like a glob of mucus. How could it be possible to isolate a single gene from this tangled mass of DNA threads? Recombinant DNA technology provides the techniques for doing just that, and today individual genes and other parts of genomes are isolated routinely.Why is gene isolation so important? First, isolation of a gene enables the determination of its nucleotide sequence. From this information, the internal landmarks of the gene can be determined—for example, intron number and position. A comparison of DNA sequences between genes also can lead to insights in gene evolution. Converting the DNA sequence of a gene into amino acid sequence by using the genetic code leads to comparisons with the protein products of known genes; and, from this knowledge, the function of the gene can often be inferred. Function can also be studied by direct modification of part of the gene's DNA sequence followed by the reintroduction of the gene into the genome. Furthermore, a gene can be moved from one organism to another. An organism containing a foreign gene is called transgenic.Transgenic organisms can be used either for basic research or for specialized commercial applications. One application has been to make valuable human gene products such as insulin in transgenic bacteria carrying the appropriate human gene. From this brief overview, we see that gene isolation has become an indispensable tool of modern genetic analysis.What are some examples of interesting genes that could be isolated? The answer depends very much on which biological process is being studied. Let's look at a few cases. A fungal geneticist studying the cellular pathway for synthesizing tryptophan would be interested in the genes that, when mutated, confer an auxotrophic requirement for tryptophan, because each gene would represent a step in the synthetic pathway <see Chapter 10>. These genes can be identified through mutation, segregation, and mapping analysis. They would be named trp1, trp2, trp3,and so forth. This geneticist would be very interested in isolating and characterizing one or more of these genes. Likewise, human genes that have mutant alleles conferring some type of functional disorder are interesting for medical and biological reasons. We have seen that these genes are identified by pedigree analysis. Two examples covered in Chapters 2 and 9 are the recessive autosomal conditions albinism and alkaptonuria. In these cases, the general nature of the defect has been understood for some time <both are enzyme defects>, but it would be very useful to isolate the genes themselves. Other human genes are known from pedigree analysis, but no biochemical function is known for them. Isolating such genes would be particularly useful because the characterization of gene structure might lead to a determination of gene function and the nature of the disease. A good example is cystic fibrosis, a disease known from pedigree analysis to be caused by an autosomal recessive allele of a gene for which no function was known until the gene was isolated and sequenced. Cases such as these would be raised in all the organisms used in genetic research.In our consideration of gene isolation, we shall first examine the nature of recombinant DNA and the principle whereby recombinant DNA technology can be used to isolate a gene. Next, we shall examine the methods for isolating specific genes such as those just discussed.Making recombinant DNAHow does recombinantDNA technology work? The organism under study, which will be usedto donate DNA for the analysis, is called the donor organism.The basic procedure is to extract and cut up DNA from a donor genome into fragments containing from one to several genes and allow these fragments to insert themselves individually into opened-up small autonomously replicating DNA molecules such as bacterial plasmids. These small circular molecules act as carriers, or vectors, for the DNA fragments. The vector molecules with their inserts are called recombinant DNA because they consist of novel combinations of DNA from the donor genome <which can be from any organism> with vector DNA from a completely different source <generally a bacterial plasmid or a virus>. The recombinantDNA mixture is then used to transform bacterial cells, and it is common for single recombinant vector molecules to find their way into individual bacterial cells. Bacterial cells are plated and allowed to grow into colonies. An individual transformed cell with a single recombinant vector will divide into a colony with millions of cells, all carrying the same recombinant vector. Therefore an individual colony contains a very large population of identical DNA inserts, and this population is called a DNA clone. A great deal of the analysis of the cloned DNA fragment can be performed at the stage when it is in the bacterial host. Later, however, it is often desirable to reintroduce the cloned DNA back into cells of the original donor organism to carry out specific manipulations of genome structure and function. Hence the protocol is often as follows:MESSAGECloning allows the amplification and recovery of a specific DNA segment from alarge, complex DNA sample such as a genome.Inasmuch as the donor DNA was cut into many different fragments, most colonies will carry a different recombinantDNA <that is, a different cloned insert>. Therefore, the next step is to find a way to select the clone with the insert containing the specific gene in which we are interested. When this clone has been obtained, the DNA is isolated in bulk and the cloned gene of interest can be subjected to a variety of analyses, which we shall consider later in the chapter. Notice that the cloning method works because individual recombinantDNA molecules enter individual bacterial host cells, and then these cells do the job of amplifying the single molecules into large populations of molecules that can be treated as chemical reagents. Figure 12-1 gives a general outline of the approach.The term recombinantDNA must be distinguished from the natural DNA recombinants that result from crossing-over between homologous chromosomes in both eukaryotes andprokaryotes. RecombinantDNA in the sense being used in this chapter is an unnatural union of DNAs from nonhomologous sources, usually from different organisms. Some geneticists prefer the alternative name chimeric DNA, after the mythological Greek monster Chimera. Through the ages, the Chimera has stood as the symbol of an impossible biological union, a combination of parts of different animals. Likewise, recombinantDNA is a DNA chimera and would be impossible without the experimental manipulation that we call recombinantDNA technology.Isolating DNAThe first step in makingrecombinantDNA is to isolate donor and vector DNA. General protocols for DNA isolation were available many decades before the advent of recombinantDNA technology. With the use of such methods, the bulk of DNA extracted from the donor will be nuclear genomic DNA in eukaryotes or the main genomic DNA in prokaryotes; these types are generally the ones required for analysis. The procedure used for obtaining vector DNA depends on the nature of the vector. Bacterial plasmids are commonly used vectors, and these plasmids must be purified away from the bacterial genomic DNA. A protocol for extracting plasmid DNA by ultracentrifugation is summarized in Figure 12-2. Plasmid DNA forms a distinct band after ultracentrifugation in a cesium chloride density gradient containing ethidium bromide. The plasmid band is collected by punching a hole in the plastic centrifuge tube. Another protocol relies on the observation that, at a specific alkaline pH, bacterial genomic DNA denatures but plasmids do not. Subsequent neutralization precipitates the genomic DNA, but plasmids stay in solution. Phages such as λalso can be used as vectors for cloning DNA in bacterial systems. Phage DNA is isolated from a pure suspension of phages recovered from a phage lysate.Cutting DNAThe breakthrough that made recombinantDNA technology possible was the discovery and characterization of restriction enzymes. Restriction enzymes are produced by bacteria as a defense mechanism against phages. The enzymes act like scissors, cutting up the DNA of the phage and thereby inactivating it. Importantly, restriction enzymes do not cut randomly; rather, they cut at specific DNA target sequences, which is one of the key features that make them suitable for DNA manipulation. Any DNA molecule, from viral to human, contains restriction-enzyme target sites purely by chance and therefore may be cut into defined fragments of a size suitable for cloning. Restriction sites are not relevant to the function of the organism, and they would not be cut in vivo, because most organisms do not have restriction enzymes.Let's look at an example: the restriction enzyme Eco RI <from E. coli> recognizes the following six-nucleotide-pair sequence in the DNA of any organism:This type of segment is called a DNA palindrome, which means that both strands have thesame nucleotide sequence but in antiparallel orientation. Many different restriction enzymes recognize and cut specific palindromes. The enzyme Eco RI cuts within this sequence but in a pair of staggered cuts between the G and the A nucleotides.This staggered cut leaves a pair of identical single-stranded "sticky ends." The ends are called sticky because they can hydrogen bond <stick> to a complementary sequence. Figure 12-3 shows Eco RI making a single cut in a circular DNA molecule such as a plasmid: the cut opens up the circle, and the linear molecule formed has two sticky ends. Production of these sticky ends is another feature of restriction enzymes that makes them suitable for recombinantDNA technology. The principle is simply that, if two different DNA molecules are cut with the same restriction enzyme, both will produce fragments with the same complementary sticky ends, making it possible for DNA chimeras to form. Hence, if both vector DNA and donor DNA are cut with Eco RI, the sticky ends of the vector can bond to the sticky ends of a donor fragment when the two are mixed.MESSAGERestriction enzymes have two properties useful in recombinant DNA technology.First, they cut DNA into fragments of a size suitable for cloning. Second, manyrestriction enzymes make staggered cuts that create single-stranded sticky endsconducive to the formation of recombinant DNA.Dozens of restriction enzymes with different sequence specificities have now been identified, some of which are shown in Table 12-1. You will notice that all the target sequences are palindromes, but, like Eco RI, some enzymes make staggered cuts, whereas others make flush cuts. Even flush cuts, which lack sticky ends, can be used for makingrecombinantDNA.DNA can also be cut by mechanical shearing. For example, agitating DNA in a blender will break up the long chromosome-sized molecules into flush-ended clonable segments.Joining DNAMost commonly, both donor DNA and vector DNA are digested with the use of a restriction enzyme that produces sticky ends and then mixed in a test tube to allow the sticky ends of vector and donor DNA to bind to each other and form recombinant molecules. Figure 12-4a shows a plasmid vector that carries a single Eco RI restriction site; so digestion with the restriction enzyme Eco RI converts the circular DNA into a linear molecule with sticky ends. Donor DNA from any other source <say, Drosophila> also is treated with the Eco RI enzyme to produce a population of fragments carrying the same sticky ends. When the two populations are mixed, DNA fragments from the two sources can unite, because double helices form between their sticky ends. There are many opened-up vector molecules in the solution, and many different Eco RI fragments of donor DNA. Therefore a diverse array of vectors carrying different donor inserts will be produced. At this stage, although sticky endshave united to generate a population of chimeric molecules, the sugar-phosphate backbones are still not complete at two positions at each junction. However, the backbones can be sealed by the addition of the enzyme DNA ligase,which create phosphodiester bonds at the junctions <Figure 12-4b>. Certain ligases are even capable of joining DNA fragments with blunt-cut ends.Amplifying recombinant DNAThe ligated recombinantDNA enters a bacterial cell by transformation. After it is in the host cell, the plasmid vector is able to replicate because plasmids normally have a replication origin. However, now that the donor DNA insert is part of the vector's length, the donor DNA is automatically replicated along with the vector. Each recombinant plasmid that enters a cell will form multiple copies of itself in that cell. Subsequently, many cycles of cell division will take place, and the recombinant vectors will undergo more rounds of replication. The resulting colony of bacteria will contain billions of copies of the single donor DNA insert. This set of amplified copies of the single donor DNA fragment is the DNA clone <Figure 12-5>.Cloning a specific geneThe foregoing descriptions are generic approaches to creating recombinant DNA. However, a geneticist is interested in isolating and characterizing some particular gene of interest, so the procedures must be tailored to isolate a specific recombinant DNA clone that will contain that particular gene. The details of the process differ from organism to organism and from gene to gene. An important initial factor is the choice of an appropriate vector for the job at hand.Choosing a cloning vectorThe ideal vector is a small molecule, facilitating manipulation. It must be capable of prolific replication in a living cell, thereby enabling the amplification of the inserted donor fragment. Another important requirement is to have convenient restriction sites that can be used for insertion of the DNA to be cloned. Unique sites are most useful because then the insert can be targeted to one site in the vector. It is also important to have a method for easily identifying and recovering the recombinant molecule. Numerous cloning vectors are in current use, and the choice between them often depends on the size of the DNA segment that needs to be cloned and on the intended application for the cloned gene. We shall consider several commonly used types.Plasmids.As described earlier, bacterial plasmids are small circular DNA molecules that are not only distinct from the main bacterial chromosome, but also additional to it. They replicate their DNA independently of the bacterial chromosome. Many different types of plasmids have been found in bacteria. The distribution of any one plasmid within a species is generally sporadic; some cells have the plasmid, whereas others do not. In Chapter 7, we encountered the F plasmid, which confers certain types of conjugative behavior to cells of E. coli. The F plasmid can be used as a vector for carrying large donor DNA inserts, as we shall see inChapter 14. However, the plasmids that are routinely used as vectors are those that carry genes for drug resistance. The drug-resistance genes are useful because the drug-resistant phenotype can be used to select not only for cells transformed by plasmids, but also for vectors containing recombinant DNA. Plasmids are also an efficient means of amplifying cloned DNA because there are many copies per cell, as many as several hundred for some plasmids.Two plasmid vectors that have been extensively used in genetics are shown in Figure 12-6. These vectors are derived from natural plasmids, but both have been genetically modified for convenient use as recombinant DNA vectors. Plasmid pBR322 is simpler in structure; it has two drugresistance genes, tet R and amp R. Both genes contain unique restriction target sites that are useful in cloning. For example, donor DNA could be inserted into the tet R gene. A successful insertion will split and inactivate the tet R gene, which will then no longer confer tetracycline resistance, and the cell will be sensitive to that drug. Therefore, the cloning procedure is to mix the samples of cut plasmid and donor DNA, transform bacteria, and select first for ampicillinresistant colonies, which must have been successfully transformed by a plasmid molecule. Of the Amp R colonies, only those that prove to be tetracycline sensitive have inserts; in other words, the Amp R Tet S colonies are the ones that contain recombinant DNA. Further experiments are needed to find the clones with the specific insert required. The pUC plasmid is a more advanced vector, whose structure allows direct visual selection of colonies containing vectors with donor DNA inserts. The key element is a small part of the E. coli β-galactosidase gene. Into this region has been inserted a piece of DNA called a polylinker or multiple cloning site, which contains many unique restriction target sites useful for inserting donor fragments. The polylinker is in frame translationally with the β-galactosidase fragment and does not interfere with its translation. The transformation protocol uses recipient cells that contain a β-galactosidase gene lacking the fragment present on the plasmid. An unusual type of complementation takes place in which the partial proteins encoded by the two fragments unite to form a functional β-galactosidase. A colorless substrate for β-galactosidase called X-Gal is added to the medium, and the functional enzyme converts this substrate into a blue dye, which colors the colony blue. If donor DNA is inserted into the polylinker, the enzyme fragment borne on the vector is disrupted, no complete β-galactosidase protein is formed, and the colony is white. Hence, selection for white Amp R colonies selects directly for vectors bearing inserts, and such colonies are isolated for further study.Small plasmids that contain large inserts of foreign DNA tend to spontaneously lose the insert; therefore, these plasmids are not useful for cloning DNA fragments larger than 20 kb.Viral vectors.Viral vectors, in which the gene or genes of interest are incorporated into the genome of a virus, offer many advantages for cloning and the subsequent applications of cloned genes. Because viruses infect cells with high efficiency, the cloned gene can be introduced into cells at a significantly higher frequency than by simple transformation. Some viral vectors are specialized for producing high levels of proteins encoded by the cloned genes, as exemplifiedby the use of insect baculovirus to express foreign proteins in a eukaryotic cell system, which is detailed in Chapter 13. Other viral vectors, such as the bacterial M13-based vectors, are designed to facilitate sequencing and the generation of mutations in cloned genes. Vectors derived from retroviruses can effect the stable integration into mammalian chromosomes of cloned DNA, allowing continued expression of the gene. Viral vectors are also the vehicles of choice for gene-therapy strategies. Some examples of viral vectors used in bacteria are described next.Phage lambda.Phage λ is a convenient cloning vector for several reasons. First, λ phage heads will selectively package a chromosome about 50 kb in length, and, as will be seen, this property can be used to select for λ molecules with inserts of donor DNA. The central part of the phage genome is not required for replication or packaging of λ DNA molecules in E. coli, so the central part can be cut out by using restriction enzymes and discarded. The two "arms" are ligated to restriction-enzyme-cut donor DNA. The chimeric molecules can be either introduced into E. coli directly by transformation or packaged into phage heads in vitro. In the in vitro system, DNA and phage-head components are mixed together, and infective λ phages form spontaneously. In either method, recombinant molecules with 10- to 15-kb inserts are the ones that will be most effectively packaged into phage heads, because this size of insert substitutes for the deleted central part of the phage genome and brings the total molecule size to 50 kb. Therefore the presence of a phage plaque on the bacterial lawn automatically signals the presence of recombinant phage bearing an insert <Figure 12-7>. A second useful property of a phage vector is that recombinant molecules are automatically packaged into infective phage particles, which can be conveniently stored and handled experimentally.Single-stranded phages.Some phages contain only single-stranded DNA molecules. On infection of bacteria, the single infecting strand is converted into a double-stranded replicative form, which can be isolated and used for cloning. The advantage of using these phages as cloning vectors is that single-stranded DNA is the very substrate required for the Sanger DNA-sequencing technique currently in widespread use <page 387>. Phage M13 is the one most widely used for this purpose.Cosmids.Cosmids are vectors that are hybrids of λ phages and plasmids, and their DNA can replicate in the cell like that of a plasmid or be packaged like that of a phage. However, cosmids can carry DNA inserts about three times as large as those carried by λ itself <as large as about 45 kb>. The key is that most of the λ phage structure has been deleted, but the signal sequences that promote phage-head stuffing <cos sites> remain. This modified structure enables phage heads to be stuffed with almost all donor DNA. Cosmid DNA can be packaged into phage particles by using the in vitro system. Cloning by cosmids is illustrated in Figure 12-8.Expression vectors.One way of detecting a specific cloned gene is by detecting its protein product expressed in the bacterial cell. Therefore, in these cases, it is necessary to be able to express the gene in bacteria; that is, to transcribe it and translate the mRNA into protein. Most cloning vectors donot permit expression of cloned genes, but such expression is possible if special vectors are used. However, because bacteria cannot process introns, the cloned sequences must be stripped of introns. The cloned gene is inserted next to appropriate bacterial transcription and translation start signals. Some expression vectors have been designed with restriction sites located just next to a lac regulatory region. These restriction sites permit foreign DNA to be spliced into the vector for expression under the control of the lac regulatory system.Making a DNA libraryWe have learned that the most important goal of recombinant DNA technology is to clone a particular gene or other genomic fragment of interest to the researcher. The approach used to clone a specificgene depends to a large degree on the gene in question and on what is known about it. Generally, the procedures start with a sample of DNA such as eukaryotic genomic DNA. The next step is to obtain a large collection of clones made from this original DNA sample. The collection of clones is called a DNA library. This step is sometimes referred to as "shotgun" cloning because the experimenter clones a large sample of fragments and hopes that one of the clones will contain a "hit"—the desired gene. The task then is to find that particular clone.There are different types of libraries, categorized, first, according to which vector is used and, second, according to the source of DNA. Different cloning vectors carry different amounts of DNA, so the choice of vector for library construction depends on the size of the genome <or other DNA sample> being made into the library. Plasmid and phage vectors carry small amounts of DNA, so these vectors are suitable for cloning genes from organisms with small genomes. Cosmids carry larger amounts of DNA, and other vectors such as YACs and BACs <see Chapters 13 and 14> carry the largest amounts of all. Ease of manipulation is another important factor in choosing a vector. A phage library is a suspension of phages. A plasmid or a cosmid library is a suspension of bacteria or a set of defined bacterial cultures stored in culture tubes or microtiter dishes.The second important decision is whether to make a genomic library or a cDNA library. cDNA,or complementary DNA, is synthetic DNA made from mRNA with the use of a special enzyme called reverse transcriptase originally isolated from retroviruses. With the use of an mRNA as a template, reverse transcriptase synthesizes a single-stranded DNA molecule that can then be used as a template for double-stranded DNA synthesis <Figure 12-9>. Because it is made from mRNA, cDNA is devoid of both upstream and downstream regulatory sequences and of introns. Therefore cDNA from eukaryotes can be translated into functional protein in bacteria—an important feature when expressing eukaryotic genes in bacterial hosts.The choice between genomic DNA and cDNA depends on the situation. If a specificgene that is active in a specific type of tissue in a plant or animal is being sought, then it makes sense to use that tissue to prepare mRNA to be converted into cDNA and then make a cDNA library from that sample. This library should be enriched for the gene in question. A cDNA library is based on the regions of the genome transcribed, so it will inevitably be smaller than a complete genomic library, which should contain all of the genome. Although genomic。
2012中级财务会计英文版第十二章-收入FA12Revenue
(1) the amount of revenue can be measured reliably; (2) it is probable that the economic benefits associated with the transaction will flow to the enterprise;
Revenue should be recognized when all the following conditions have been satisfied:
(1) the enterprise has transferred to the buyer the significant risks and rewards of ownership of the goods;
Revenue should be recognized on the following bases:
(1) interest should be recognized on a time proportion basis that takes into account the effective yield on the asset;
Revenue should be measured at the fair value of the consideration received or receivable.
revenue for service
If the outcome of the transaction can be estimated reliably, companies recognize revenues using Percentage-of-Completion Method. 1、The outcome of the transaction can be estimated reliably when all the following conditions are satisfied:
第十二章 杂环化合物
当环上连有烷基、硝基、卤素、羟基、氨基等取代基时，以杂环为母体； 当环上连有醛基、羧基、磺酸基时，将杂环作为取代基，取代基位置用 数字编号，杂原子编号应最小。
CHO O
2-呋喃甲醛 2-furancarboxaldehyde
NO2
S
3-硝基噻吩 3-nitrothiophene
CH3
N
4-甲基吡啶 4-methylpyridine
N 吡啶 Pyridine
含二个杂原子
N
N 嘧啶 Pyrimidine
O 吡喃 pyran
N
N 吡嗪
pyrazine
2
五元杂环与 苯环稠合
O
苯并呋喃 benzofunan
稠杂环
六元杂环与 苯环稠合
N
喹啉 quinoline
杂环与杂 环稠合
N
N
N
N
H
嘌呤 purine
N H
吲哚 indole
N
S 苯并噻唑 benzothiophene
苯炔
H2, Pd
N H
N H
H2 , MoS2
S
S
H2 , Ni
15
3、呋喃、吡咯和噻吩环的制法
呋喃容易从糠醛去羰基得到：
O
CHO ＋ H2O
ZnO-Crபைடு நூலகம்O3 400℃
+ CO2 + H2O O
噻吩可以用丁烷或丁烯与硫磺加热反应得到：
CH3CH2CH2CH3+ 4S 600℃
＋ 3H2S S
以氧化铝为催化剂，可以实现呋喃、吡咯和噻吩环的互变 （Yuyev反应）
E H
E H +N H
商务英语口译第12章
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民意C调o查py：ripguhbtlic20op0i4ni-o2n0p1o1llsAspose Pty Ltd.
改善民生：improve people’s livelihood 修订上市原则：amend the listing rules 建立共识：reach a consensus 电子政府服务：e-Government services
Hands across diEvvisailuona:t跨ion部o门n参ly.与 ted with Aspose.Slides for .NET 3.5 Client Profile 5.2
StraCteogpyyrgiogahlts2:战00略4目-2标011 Aspose Pty Ltd.
Slow-moving bureaucracies:拖沓的官僚机构 Chain of command：行政管理系统
第十二章 经营管理
Chapter 12 BusinEveaslsuaMtioannoanglye.ment
ted with Aspose.Slides for .NET 3.5 Client Profile 5.2 Copyright 2004-2011 Aspose Pty Ltd.
《英语语法》第十二章 关系分句
第十二章关系分句限制性与非限制性关系分句分两种：限制性关系从句与非限制性关系从句。
这两种关系分句的划分非常重要，因为它们不仅形式不同，作用也不同。
①Jilian Brown.who lives next door is travelling in Scotland.吉连·布朗，住在隔壁，现在正在苏格兰旅行。
②The girl who lives next door is now travelling in Scotland.住在隔壁的那个女孩子现在正在苏格兰旅行。
③Anne returned my book to the library by mistake, whichJ bought at a bookstore at Cambridge.安妮误把我的书错还给图书馆了，那本书是我在剑桥一个书店买的。
④This is the book(which／that) I bought at a bookstore at Cambridge.这是我在剑桥一个书店买的书。
首先，在①和③中的非限制性关系分句在书写时用逗号隔开，在口语中有轻微的停顿和前后语调的变化。
在句②和④中的限制性关系分句没有这些特征。
其他形式上的区别还包括代词的选择。
如果一个分句是象④句中那样由that来引导（或者是萋羞运贫词歹，那么这个分句一定是限制性关系分句。
但如果是象③句中那样由which引导（或其他wh-词），那么它可能是限制性也可能是非限制性关系分句。
鬯乡趸拳思王韭堡型关系分句中。
其次，两种关系分句作用不同。
限制性关系分句是名词词组不可分割的一部分，为确定先行项的所指对象提供必不可少的信息。
在句②中女孩的身份决定于她的住址。
句④也一样，其中关系分句为书的所指对象提供必不可少的信息。
另一方面，非限定性关系分句只提供那些对确定我们所谈论的人或物的所指对象来说不需要的附加信息，所以，如果省略了非限定性关系分句，并不影响先行项的所指意义。
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Slide85-8
Preview
The basics of exchange rates Exchange rates and the prices of goods The foreign exchange markets The demand for foreign currency assets A model of foreign exchange markets
CTBU Liu Rong
Slide85-7
Some hot issues
/watch?v=_VE6x6zIHds&feature=us er /f/200809/e76b3e60-f496-4f9d-b4d29e014839a920.shtml /news/video/200809/0917_4460_788 362.shtml /ap/financialnews/D9374SM G0.htm /s/afp/20080915/bs_afp/useconomym arketsfinancebankbanking /f/200809/09548796-39c8-4a18-80968dfdf8378764.shtml
CTBU Liu Rong
Slide85-2
c. If foreign official capital inflows to Pecunia were $600 million, the country had a balance of payments surplus of $100 million. Put another way, the country needed only $1 billion to cover its current-account deficit, but $1.1 billion flowed into the country. The Pecunian central bank must, therefore, have used the extra $100 million in foreign borrowing to increase its reserves. Purchases of Pecunian assets by foreign central banks enter their countries' balance of payments accounts as outflows, which are debit items. The rationale is that the transactions result in foreign payments to the Pecunians who sell the assets.
CTBU Liu Rong
Slide85-4
Chapter 13 Exchange Rates and the Foreign Exchange Market: An Asset Approach
International Economics: Theory and Policy, Sixth Edition by Paul R. Krugman and Maurice Obstfeld
CTBU Liu Rong
Slide85-1
b. By dipping into its foreign reserves, the central bank of Pecunia financed the portion of the country's currentaccount deficit not covered by private financial inflows. Only if foreign central banks had acquired Pecunian assets could the Pecunian central bank have avoided using $500 million in reserves to complete the financing of the current account. Thus, Pecunia's central bank lost $500 million in reserves, which would appear as an official financial inflow (of the same magnitude) in the country's balance of payments accounts.
CTBU Liu Rong
Slide85-12
/huobizhengce/huobizhengcegongju/ huilvzhengce/renminbihuilvjiaoyishoupanjia.asp /other/quotation.jsp /cmb2005forex/forexaspxbin/forex_ hq/realrate.aspx /currency/convert?from=USD&to =CAD&amt=1&t=5y /market/ /column/waihui/index.html
relative to another currency.
• A depreciated currency is less valuable (less
expensive) and therefore can be exchanged for (can buy) a smaller amount of foreign currency.
Ans to Q5-Ch12
a.
the balance of payments of Pecunia (official settlements balance) was -$500 million. The country as a whole somehow had to finance its $1 billion current-account deficit, so Pecunia's net foreign assets fell by $1 billion.
• role of interest rates • role of expectations about the exchange rates
CTBU Liu Rong Slide85-9
Definitions of Exchange Rates
Exchange rates are quoted as foreign currency per
¥3,000,000 • Or, ¥3,000,000 x $0.0094/¥1 = $28,200
CTBU Liu Rong
Slide85-14
Depreciation and Appreciation
Depreciation is a decrease in the value of a currency
unit of domestic currency or domestic currency per unit of foreign currency.
• How much can be exchanged for one dollar?
RMB6.84/$1 • How much can be exchanged for one Chinese Yuan? ?/RMB1
CTBU Liu Rong
Slide85-13
•
Exchange rate allow us to denominate the cost or price of a good or service in a common currency.
• How much does a Honda cost? Japanese yen
• $1/€1 $1.47/€1 means that the dollar has
depreciated relative to the euro. It now takes $1.47 to buy one euro, so that the dollar is less valuable.
• The euro has appreciated relative to the dollar:
CTBU Liu Rong
Slide85-3
d.
Along with non-central bank transactions, the accounts would show an increase in foreign official reserve assets held in Pecunia of $600 million (a financial account credit, or inflow) and an increase Pecunian official reserve assets held abroad of $100 billion (a financial account debit, or outflow). Of course, total net financial inflows of $1 billion just cover the current-account deficit.
JPY DEM FRF EUR SEK CHF GBP
Slide85-11
Exchange Rates
An exchange rate can be quoted in two ways:
• Indirect •
•
– The price of the foreign currency in terms of home currency Direct – The price of home currency in terms of the foreign currency Example: USD 1= RMB 6.85 is an indirect quote for the U.S. dollar, but a direct quote for RMB.