专业英语翻译答案
材料科学与工程专业英语第三版-翻译以及答案
UNIT 1一、材料根深蒂固于我们生活的程度可能远远的超过了我们的想象，交通、装修、制衣、通信、娱乐（recreation）和食品生产，事实上（virtually），我们生活中的方方面面或多或少受到了材料的影响。
历史上，社会的发展和进步和生产材料的能力以及操纵材料来实现他们的需求密切（intimately）相关，事实上，早期的文明就是通过材料发展的能力来命名的（石器时代、青铜时代、铁器时代）。
二、早期的人类仅仅使用（access）了非常有限数量的材料，比如自然的石头、木头、粘土（clay）、兽皮等等。
随着时间的发展，通过使用技术来生产获得的材料比自然的材料具有更加优秀的性能。
这些性材料包括了陶瓷（pottery）以及各种各样的金属，而且他们还发现通过添加其他物质和改变加热温度可以改变材料的性能。
此时，材料的应用（utilization）完全就是一个选择的过程，也就是说，在一系列有限的材料中，根据材料的优点来选择最合适的材料，直到最近的时间内，科学家才理解了材料的基本结构以及它们的性能的关系。
在过去的100年间对这些知识的获得，使对材料性质的研究变得非常时髦起来。
因此，为了满足我们现代而且复杂的社会，成千上万具有不同性质的材料被研发出来，包括了金属、塑料、玻璃和纤维。
三、由于很多新的技术的发展，使我们获得了合适的材料并且使得我们的存在变得更为舒适。
对一种材料性质的理解的进步往往是技术的发展的先兆，例如：如果没有合适并且没有不昂贵的钢材，或者没有其他可以替代（substitute）的东西，汽车就不可能被生产，在现代、复杂的（sophisticated）电子设备依赖于半导体（semiconducting）材料四、有时，将材料科学与工程划分为材料科学和材料工程这两个副学科（subdiscipline）是非常有用的，严格的来说，材料科学是研究材料的性能以及结构的关系，与此相反，材料工程则是基于材料结构和性能的关系，来设计和生产具有预定性能的材料，基于预期的性能。
英语专业八级考试翻译部分历届试题及参考答案
1995年英语专业八级考试简.奥斯丁的小说都是三五户人家居家度日，婚恋嫁娶的小事。
因此不少中国读者不理解她何以在西方享有那么高的声誉。
但一部小说开掘得深不深，艺术和思想是否有过人之处，的确不在题材大小。
有人把奥斯丁的作品比作越咀嚼越有味道的橄榄。
这不仅因为她的语言精彩，并曾对小说艺术的发展有创造性的贡献，也因为她的轻快活泼的叙述实际上并不那么浅白，那么透明。
史密斯夫人说过，女作家常常试图修正现存的价值秩序，改变人们对“重要”和“不重要”的看法。
也许奥斯丁的小说能教我们学会转换眼光和角度，明察到“小事”的叙述所涉及的那些不小的问题。
参考译文：颜林海Jane Austin’s novels tell about such things unimportant as life, love and marriage in a few families that many Chinese readers do not understand why she has enjoyed such a high reputation in the western countries. But subject matter is indeed not the decisive factor by which we can judge whether or not a novel has its depth, or whether or not it has something superior to others in its artistic appeal and ideological content. Some people compare Austin’s works to olives: the more you chew them, the tastier you feel them. It is not only because of her wonderful language as well as her creative contribution to the development of novel writing as an art, but also because of something that her light and lively narrative hides——something implicit and opaque. Mrs Smith once said, women writers often tried to rectify the existing value orders, and to change people’s opinions on “what’s important or not”. Maybe Austin’s novels can teach us how to change our perspective and vision, really to dig those things important through the narrative of the ones unimportant.E-C原文I, by comparison, living in my overpriced city apartment, walking to work past putrid sacks of street garbage, paying usurious taxes to local and state governments I generally abhor, I am rated middle class. This causes me to wonder, do es the measurement make sense? Are we measuring only that which is easily measured--- the numbers on the money chart --- and ignoring values more central to the good life? For my sons there is of course the rural bounty of fresh-grown vegetables, line-caught fish and the shared riches of neighbours’orchards and gardens. There is the unpaid baby-sitter for whose children my daughter-in-law baby-sits in return, and neighbours who barter their skills and labour. But more than that, how do you measure serenity? Sense of self?I don’t want to idealize life in small places. There are times when the outside world intrudes brutally, as when the cost of gasoline goes up or developers cast their eyes on untouched farmland. There are cruelties, there is intolerance, there are all the many vices and meannesses in small places that exist in large cities. Furthermore, it is harder to ignore them when they cannot be banished psychologically to another part of town or excused as the whims of alien groups --- when they have to be acknowledged as “part of us.”Nor do I want to belittle the opportunities for small decencies in cities --- the eruptions of one-stranger-to-another caring that always surprise and delight. But these are, sadly, more exceptions than rules and are often overwhelmed by the awful corruptions and dangers that surround us.比较而言，我住在在收费不菲的城市公寓里，步行去工作还得经过恶臭的街头圾袋，向我一向讨厌的地方政府和州政府缴纳高利贷式税收，竟然还被认定为中产阶级。
(word完整版)材料科学与工程专业英语第三版-翻译以及答案
UNIT 1一、材料根深蒂固于我们生活的程度可能远远的超过了我们的想象,交通、装修、制衣、通信、娱乐(recreation）和食品生产，事实上（virtually）,我们生活中的方方面面或多或少受到了材料的影响。
历史上，社会的发展和进步和生产材料的能力以及操纵材料来实现他们的需求密切（intimately）相关，事实上，早期的文明就是通过材料发展的能力来命名的(石器时代、青铜时代、铁器时代）。
二、早期的人类仅仅使用（access）了非常有限数量的材料，比如自然的石头、木头、粘土（clay）、兽皮等等.随着时间的发展，通过使用技术来生产获得的材料比自然的材料具有更加优秀的性能。
这些性材料包括了陶瓷(pottery)以及各种各样的金属，而且他们还发现通过添加其他物质和改变加热温度可以改变材料的性能。
此时，材料的应用(utilization）完全就是一个选择的过程，也就是说，在一系列有限的材料中，根据材料的优点来选择最合适的材料，直到最近的时间内，科学家才理解了材料的基本结构以及它们的性能的关系。
在过去的100年间对这些知识的获得,使对材料性质的研究变得非常时髦起来。
因此,为了满足我们现代而且复杂的社会，成千上万具有不同性质的材料被研发出来,包括了金属、塑料、玻璃和纤维.三、由于很多新的技术的发展，使我们获得了合适的材料并且使得我们的存在变得更为舒适。
对一种材料性质的理解的进步往往是技术的发展的先兆，例如:如果没有合适并且没有不昂贵的钢材，或者没有其他可以替代（substitute）的东西,汽车就不可能被生产，在现代、复杂的（sophisticated）电子设备依赖于半导体（semiconducting）材料四、有时，将材料科学与工程划分为材料科学和材料工程这两个副学科(subdiscipline）是非常有用的，严格的来说，材料科学是研究材料的性能以及结构的关系，与此相反,材料工程则是基于材料结构和性能的关系，来设计和生产具有预定性能的材料，基于预期的性能。
材料科学与工程专业英语第三版-翻译以及答案
UNIT 1一、材料根深蒂固于我们生活的程度可能远远的超过了我们的想象，交通、装修、制衣、通信、娱乐（recreation）和食品生产，事实上（virtually），我们生活中的方方面面或多或少受到了材料的影响。
历史上，社会的发展和进步和生产材料的能力以及操纵材料来实现他们的需求密切（intimately）相关，事实上，早期的文明就是通过材料发展的能力来命名的（石器时代、青铜时代、铁器时代）。
二、早期的人类仅仅使用（access）了非常有限数量的材料，比如自然的石头、木头、粘土（clay）、兽皮等等。
随着时间的发展，通过使用技术来生产获得的材料比自然的材料具有更加优秀的性能。
这些性材料包括了陶瓷（pottery）以及各种各样的金属，而且他们还发现通过添加其他物质和改变加热温度可以改变材料的性能。
此时，材料的应用（utilization）完全就是一个选择的过程，也就是说，在一系列有限的材料中，根据材料的优点来选择最合适的材料，直到最近的时间内，科学家才理解了材料的基本结构以及它们的性能的关系。
在过去的100年间对这些知识的获得，使对材料性质的研究变得非常时髦起来。
因此，为了满足我们现代而且复杂的社会，成千上万具有不同性质的材料被研发出来，包括了金属、塑料、玻璃和纤维。
三、由于很多新的技术的发展，使我们获得了合适的材料并且使得我们的存在变得更为舒适。
对一种材料性质的理解的进步往往是技术的发展的先兆，例如：如果没有合适并且没有不昂贵的钢材，或者没有其他可以替代（substitute）的东西，汽车就不可能被生产，在现代、复杂的（sophisticated）电子设备依赖于半导体（semiconducting）材料四、有时，将材料科学与工程划分为材料科学和材料工程这两个副学科（subdiscipline）是非常有用的，严格的来说，材料科学是研究材料的性能以及结构的关系，与此相反，材料工程则是基于材料结构和性能的关系，来设计和生产具有预定性能的材料，基于预期的性能。
专业英语八级(翻译)模拟试卷23(题后含答案及解析)
专业英语八级（翻译）模拟试卷23(题后含答案及解析) 题型有： 5. TRANSLATIONPART V TRANSLATION (60 MIN)SECTION A CHINESE TO ENGLISHDirections: Translate the following text into English.1．择书比择友简单得多。
不善辞令、厌恶应酬的人，可以自由自在地徜徉于书林之中，游目四顾，俯拾皆友。
看书，可以博览，可以细嚼，没有人会怪你喜新厌旧，也没有人要求你从一而终。
你大可以从一本换到另一本，喜爱的书，不妨一读再读；不耐看的书，又可随手抛下，谁也不会因此而伤心失望。
人际关系错综复杂，那“书际关系”呢?只要花点时间去了解，再高深的学问也弄得明白。
正确答案：It is much easier to choose a book than a friend. One who is poor at speech and shuns socializing will nevertheless feel like being surrounded by friends while sauntering freely in the midst of books. Some books are to be read cursorily, and some are to be chewed and digested. None will ever call you fickle-minded, and none will ever demand that you be constant in your affection. You can go from one book to another. And you can read your favorite book over and over again. When you lay aside the book you dislike, none will ever feel hurt or disappointed. While interpersonal relations are very complicated, what about your relations with books? Devote your time to studies, and you will be able to acquire any knowledge no matter how profound it is.解析：1、这两段为论说性小品文，整体时态应为一般现在时。
新编英语教材5翻译答案(英语专业)
Unit 101.John Dewey has said in all seriousness that the part played by custom in shaping the behaviour of the individual as over against any way in which he can affect traditional custom, is as the proportion of the total vocabulary of his mother tongue over against those words of his own baby talk that are taken up into the vernacular of his family.答案：John Dewey has pointed out seriously that how far a social habit can impact an individual behavior as compared with how far an individual behaviour can impact a social habit can be likened to how far a native language can affect the entire vocabulary of a family dialect as compared with how far the entire vocabulary of a family dialect can affect a native language.2.When one seriously studies the social orders that have had the opportunity to develop autonomously ,the figure becomes no more than an exact and matter-of-fact observation.答案：The result from a serious study of various cultures that are allowed to grow with no influence from outside proves to be in complete conformity with the reality.3.Anthropology was by definition impossible as long as these distinctions between ourselves and the primitive,ourselves and the barbarian,ourselves and the pagan,held sway over people’s minds. 答案：No scientific study of people and their cultures can be expected to achieve any fruitful end,where we still strongly believe that ours is superior to other cultures,which we have traditionally considered as underdeveloped,uncivilized or irreligious.4.It was necessary to recognize that these institutions which are based on the same premises,let us say the supernatural,must be considered together,our own among the rest.答案：We should accept that these cultures,which are like ours created by God,must be treaded as equals to our own culture and included in our study of social customs.Unit 111.Up above me,I knew,were unselfishnesses of the spirit,clean and noble thinking, keen intellectual living.答案：I believed that in a society high above me lived those who selfless,noble-minded and well-cultivated.2.But it is not particularly easy for one to climb up out of the working-class-especially if he is handicapped by the possession of ideals and illusions.答案：But it is surely difficult for a man,especially one full of objectives and imagination in life,to have his working class status changed.3.I had the muscle,and they made money out of it while I made but a very indifferent living out of it.答案：I was physically strong,and they profited by the exploitation of my physical strength,which,to my great disappointment, was not able to change my life for the better.4.He was a muscle bankrupt, and nothing remained to him but to go down into the cellar of society and perish miserably.答案：He was no longer physically strong/powerful,his strength was used up/exhausted/consumed completely /wore out;and he had to let himself slide down to the bottom of society,left alone in misery till the end of his life.1.One hundred years later,the Negro is still languished in the corners of American society and finds himself an exile in his own land.答案：One hundred years later,the Negro still lives in a land of poverty isolated from a land of immense /enormous wealth,which surrounds us and is our homeland.2.It is obvious today that America has defaulted on this promissory note insofar as her citizens of color are concerned.答案：We can see clearly now that America has failed to execute this document as promised,as far as the black people are concerned.3.So we have come to cash this check-a check that will give us upon demand the riches of freedom and the security of justice.答案：So we are here to demand the fulfillment of a promise which assures us of liberty and justice.4.This is no time to engage in the luxury of cooling off or to take the tranquilizing drug of gradualism.答案：This is not the time now to try to persuade us to keep quiet and wait patiently,by and by, a solution is eventually found.Unit 21.Moses pleaded a speech defect to rationalize his reluctance to deliver Jehovah’s edict to Pharaoh.答案：Moses justified his unwillingness to pass Jehovah’s order to Pharaoh,saying that he was “slow of speech”.2.Yet for all the trouble procrastination may incur,delay can often inspire and revive a creative soul.答案：Delay leads to problems.However,in many cases,it can often stimulate the creativity in an artist.3.He notes that speedy action can be embarrassing or extremely costly.答案：He points out that hastiness may give rise to decisions which turn out to be humiliating or expensive.4.Bureaucratization,which flourished amid the growing burdens of government and the greater complexity of society,was designed to smother policymakers in blankets of legalism,compromise and reappraisal-and thereby prevent hasty decisions from being made.答案：Excessive red-tape developed because public administration was expanding in scope and because society was growing more and more complicated.In this sense,red-tape helped those in charge of policy to be fully engaged in an enormous amount of paperwork and judgement,thus making it impossible for an immature decision to result.5....many of my friends go through agonies when they face a blank page.答案：...many of my friends have a hard time the moment they attempt to put pen to paper.Unit 131.People who are partial to euphemisms stand accused of being “phony”or trying to hide what it is they are really talking about.答案：Euphemism-prone people are subject to the charge that they are insincere.2.What we call things affects how we will perceive them.答案：Things may take on a different look when named differently.3.It would appear that human beings almost naturally come to identify names with things,which is one of our more fascinating illusions.答案：It seems that mankind is predisposed to regard things as being inseparable from the labels they bear.This is a most intriguing delusion.4.For if you change the names of things,you change how people will regard them,and that is as good as changing the nature of the thing itself.答案：With the change of the names of things,you have changed their images in the eye of people,which,in effect,means a change in what the things really are.5.The teacher who prefers us to use the term”culturally different children”instead of “slum children”is euphemizing,all right,but is doing it to encourage us to see aspects of a situation that might otherwise not be attended to.答案：It is true that the teacher is euphemizing when he has us use”culturally different children” in place of “slum children”, but what he is doing is to try to turn our attention to an aspect of life that might easily be neglected.6.Saying that someone is “dead”is not to speak more plainly or honestly than saying he has “passed away”.答案：People are just as frank when they say someone “passed away”as when they say he is “dead”.Unit 151.Most previous analogies are seriously inadequate, for while they may describe a part of the teaching activity,they also suggest patterns that are not fully applicable to teaching.答案：Almost none of the analogies that have been used so far can fully describe what teaching is all about.(or: Nearly all the analogies that have been used so far can only present a partial picture,rather than a complete one,of what teaching is really about.)In this sense,none of them serves as an analogy for teaching.2.Rather than emphasizing the mutuality of the endeavor,each of these common analogies turns ona separation between the professional and his clients.答案：Each of these popular analogies sees the teacher and his students not as an organic unit tied together in a joint effort,but as being isolated from each other.3.The teacher as actor also plays to a passive audience,but he measures success by large numbers. 答案：The teacher,seen in the role of the actor,would be simply lecturing to an audience ,who do not participate, and he would evaluate his performance not by their involvement in class activities,but by the size of the class.4.The mountaineer accepts his leadership role,yet recognizes that the success of the journey(measured by the scaling of the heights)depends upon close cooperation and active participation by each member of the group.答案：The mountaineer knows his own function as a leader and is well aware,too,that whether they can climb to the top is decided by how well each member can cooperate with the others and how far each member is ready to involve himself in the endeavour.5.Essential skills must be mastered if the trip is to be successful;lacking them,disaster looms as anominous possibility.答案：For a good journey,basic skills from an indispensable part,without which one is likely to encounter misfortune.翻译1.习俗不同于传统在于前者是一个社会中公认的行为规范，而后者则是指从过去传到现在的思维和行为的习惯方式。
电子信息专业英语课文翻译和答案
第一单元元件与定律A．课文译文电阻器、电容器和电感器在电子电路中，电阻器、电容器和电感器是特不重要的元件。
电阻器和电阻电阻器是二端口元件。
电阻是阻止电流流淌，更确切地讲，是阻止电荷流淌的能力。
在国际单位制中，电阻用欧姆来度量。
希腊字母Ω是欧姆的标准符号。
较大的电阻一般用千欧和兆欧来表示。
模拟这种特性常用的电路元件是电阻器。
图1.1表示电阻器的电路符号，R表示电阻器的电阻值。
图1.1电阻器的电路符号为了进行电路分析，我们必须在电阻器中指明电流和电压的参考方向。
要是我们选择关联参考方向，那么电压和电流之间的关系是：v=iR(1.1) 那个地点v是电压，其单位是伏特，i是电流，其单位是安培，R是电阻，其单位是欧姆。
要是选择非关联参考方向，我们必须写成：v=－iR(1.2) 用在公式〔1.1〕和〔1.2〕中的代数式确实是根基闻名的欧姆定律。
欧姆定律表示了电压作为电流的函数。
然而，要表示电流是电压的函数也是特不方便的。
欧姆定律是电阻两端的电压和电流间的代数关系。
电容器和电容电能能够存储在电场中，存储电能的装置喊电容器。
电容器存储电能的能力喊做电容。
图1.2表示电容器的电路符号。
电容的电路参数用字母C表示，用法拉来度量。
因为法拉是相当大的电容量，实际上电容值通常位于皮法和微法之间。
图1.2电容器的电路符号当电压随时刻变化时，电荷的位移也随时刻变化，引起了众所周知的位移电流。
在终端，位移电流和传导电流没有区不。
当电流参考方向和电压参考方向是关联参考方向时，电流正比于电容两端电压随时刻的变化率的数学表达式为： dt dv C i =(1.3) 那个地点i 的单位是安培，C 的单位是法拉，v 的单位是伏特，t 的单位是秒。
电感器和电感众所周知，电感是电子电路中的模块之一。
所有的线圈都有电感。
电感是反抗流过线圈电流的任何变化的性质。
电感用字母L 表示，其单位是亨利。
图1.3表示一个电感器。
图1.3电感器的电路符号当电流和电压的参考方向关联时，有dtdi L v =(1.4) 那个地点v 的单位是伏特，L 的单位是亨利，i 的单位是安培，t 的单位是秒。
(完整word版)汽车专业英语翻译及课后答案--黄韶炯(全部单元都有) (2)
Unit 1 Automotive BasicsAutomobiles， trucks, and buses are essential forms of transportation. They are complex machines made up of many parts. These parts can be grouped into a number of systems. An understanding of how the system work will help you understand how the automobile works.轿车、卡车和客车是交通运输的重要组成部分.它们都是由许多部件组成的复杂机器.这些部件可以归类为汽车的几个组成系统。
了解这些各个小系统是如何工作的将有助于我们理解整个汽车系统是如何工作。
An automobile can be divided into two basic parts： a body and a chassis. The body is the enclosure that houses the engine， passengers， and cargo。
It is the part of the automobile that you see。
The chassis is that part of the automobile beneath the body。
汽车可以分为两个基本部分：车身和底盘。
车身包围发动机、乘客和行李，它是汽车你所看到的部分。
而车身以下的部分就是底盘.1.1 THE BODY An automobile body is a sheet metal shell with windows， doors， a hood, and a trunk deck built into it。
It provides a protective covering for the engine， passengers， and cargo。
(完整)英语专业综合教程课后习题中译英翻译答案
1.我安排他们在小酒吧见面，但那小伙子一直都没有来。
（turn up）1. I had arranged for them to meet each other at the pub but the young man never turned up.2你无法仅凭表象判断形势是否变得对我们不利。
（tell from appearance)2. You cannot tell merely from appearance whether things will turn out unfavourable to us or not.3.那个士兵每次打仗都冲锋在前，从而赢得了最高荣誉。
（stand in the gap）3. The soldier, who stood in the gap in every battle, gained the highest honors if the country.4.主席讲话很有说服力，委员会其他成员都听从他的意见。
（yield to）4. The chairman spoke so forcefully that the rest of the committee yielded to his opinion.5.他们现在生活富裕了，但也曾经历坎坷。
(ups and down)5. They are well-to-do now, but along the way they had their ups and downs.6.这次演讲我说明两个问题。
(address oneself to)6. There are two questions to which I will address myself in this lecture.7.我们正在筹划为你举办一次盛大的圣诞聚会。
(in somebody's honour)7. We are planning a big Christmas party in your honor.8.听到那个曲子，我回想起了而同时代。
应用化学专业英语(课后答案和课文翻译)
应用化学专业英语(课后答案和课文翻译)Unit 1 The Roots of Chemistry I. Comprehension.1.It can be inferred from this article which one of the following items is not mainly based on practical use C. Greek chemistry2. It was B. Empedocless who first introduced the idea that all things are not formed from just one element.3. In the development of Greek chemistry, D. Democritus was the first one definiting the ultimately constituents of matter?4. According to Plato, there are B. 4 �Delements‖ whose faces are constituted by regular polygons.5. In the last paragraph,authors think that experiment DD.can deal with the reactions by which one substance is converted into anotherII. Make a sentence out of each item by rearranging the words in brackets.1. The purification of an organic compound is usually a matter of considerable difficulty, and itis necessary to employ various methods for this purpose.2. Science is an ever-increasing body of accumulated and systematized knowledge and is also anactivity by which knowledge is generated.3. Life, after all, is only chemistry, in fact, a small example of chemistry observed on a singlemundane planet.4. People are made of molecules; some of the molecules in people are rather simple whereasothers are highly complex.5. Chemistry is ever present in our lives from birth to death because without chemistry there isneither life nor death.6. Mathematics appears to be almost as humankind and also permeates all aspects of human life,although many of us are not fully aware of this.III. Translation.1. (a)化学过程； (b)自然科学；（c）蒸馏技术(a) chemical process (b) natural science (c) the technique ofdistillation 2. 正是原子构成铁、水、氧等。
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The information encoded in genetic material (DNA) is responsible for establishing and maintaining the celluar and biochemical functions of an organism.编码信息的遗传物质DNA负责建立和维持细胞和一个生物体的生物化学功能。 In most organisms, the DNA is an extended double-stranded polymer.在大多数生物体内，DNA是延伸的双链聚合物。 The sequence of units (deoxyribonucleotides) of one DNA strand is complementary to the deoxyribonucleotides of the other strand.一条DNA链的脱氧核苷酸序列与另一条的脱氧核苷酸序列互补。 This complementarity enables new DNA molecules to be synthesized with the same linear array of deoxyribonucleotides in each strand as an original DNA molecule. 这种互补性能够合成与最初始DNA分子每一条链相同的脱氧核苷酸序列的新的DNA分子。The process of DNA synthesis is called replication.这个DNA合成的过程叫做复制。 A specific order of deoxyribonucleotides determines the information content of an individual genetic element (gene). 一个特定的脱氧核苷酸顺序决定一个单独的遗传元素（基因）的信息内容。Some genes encode proteins ,and others encode only ribonucleic acid (RNA) molecules.一些基因编码蛋白质，另一些只编码核糖核酸（RNA）分子 The protein-coding genes (structural genes) are decoded by two successive major cellular processes: RNA synthesis (transcription) and protein synthesis (translation). First, a messenger RNA (mRNA) molecule is synthesized from a structural gene. Second, an individual mRNA molecule interacts with other components, including ribosomes, transfer RNAs (tRNAs) , and enzymes, to produce a protein molecule.翻译蛋白质的基因（结构基因）通过两个连续的主要细胞过程进行翻译：RNA合成（转录）和蛋白质合成（翻译）。首先，信使RNA分子从结构基因上被合成，然后，这个mRNA分子和其他组分包括核糖体，转运RNAs和酶相互作用来生产一个蛋白质分子。 A protein consists of a precise sequence of aminoacids which is essential for its activity.一个蛋白质是由一个精确的氨基酸序列组成，这个氨基酸序列对于蛋白质的活动是必须的。 Molecular biotechnologists use genes from a variety of organisms to create beneficial products. 利用基因分子技术从不同的有机体创造有利的产品。To understand how this is accomplished, it is helpful to know about the structure of DNA, replication, transcription, and translation.去理解这是怎样完成的，它是有帮助的去了解DNA的结构，复制，转录和翻译。 The chemistry of DNA has been studied since 1868. By the 1940s, it was known that DNA was made up of individual units called nucleotides that are linked to each other to form long chains. A nucleotide consists of an organic base (base), a five-carbon sugar (pentose), and a phosphate group. 自从1986年DNA的化学性质就已经被研究了，到了1940年代，DNA是由叫做核苷酸的个别单位相互联系形成长链组成的是被知道的，一个核苷酸是由一个碱基，一个五碳糖和一个磷酸基组成。The phosphate group and organic base are attached to the 5’ carbon and 1’carbon atoms of the sugar moiety, respectively. 磷酸基和碱基分别与糖基的5‘碳原子和1’碳原子连接。In DNA, there are four kinds of organic bases: adenine (A), guanine (G), cytosine (C), and thymine (T). DNA有四种碱基：腺嘌呤，鸟嘌呤，胞嘧啶，胸腺嘧啶。The sugar of DNA is 2’-deoxyribose because it has a hydroxyl (-OH) group only on the 3’carbon of the sugar moiety.DNA的糖是2‘脱氧核糖因为它仅仅在糖基的3’碳上有一个羟基组。 By contrast, ribose, which is another five-carbon sugar, has hydroxyl groups at both the 2’ and 3’ carbons of the pentose ring. 相反，核酸糖是另一种五碳糖，在戊糖环的2‘和3’碳原子上有羟基团。The nuleotides of DNA are joined by phosphodiester bonds, with the phosphate group of the 5’ carbon of one nucleotide linked to the 3’ –OH group of the deoxyribose of adjacent nucleotide.核苷酸通过磷酸二脂键连接，即一个核苷酸的5‘碳原子的磷酸基与相邻的核苷酸脱氧核糖的3’羟基相连接。 A polynuleotide strand has a 3’-OH group at one end (3’ end) and a 5’ phosphate group at the other (5’ end).一个多核苷酸链的一个末端是3‘羟基团另一端是5‘磷酸基团。 In 1953, James Waston and Francis Crick, using X-ray diffraction analysis of crystallized DNA, discovered that native DNA consists of two long chains (strands) that form a double-stranded helix. 1953年，詹姆斯.沃森和弗朗西斯.克里克，利用x射线衍射分析结晶的DNA，发现天然DNA包含两个长链，形成一个双链螺旋The coiled polynucleotide chains of DNA are held together by hydrogen bonds between the bases of the opposite strands. The bases occur as specific sets of complementary pairs.DNA盘绕的多核苷酸链是由相反链的碱基之间的氢键支撑的A pairs only with T, and G pairs only with C.A与T配对，G与C配对。 The A· T base pairs are held together by two hydrogen bonds, and the G· C base pairs are held together by three.A.T碱基对间有两个氢键，G.C碱基对间有三个氢键。 The number of complementary base pairs (bp) is often used to characterize the length of a double-stranded DNA molecule.互补碱基对的数量经常被用来描述一个双链DNA分子的长度。 For DNA molecules with thousands or millions of base pairs, the designations are kilobase pairs (kb) or megabase pairs (Mb) , respectively.对于数千或数百万碱基对的DNA分子 分别用kb或mb的单位。For example, the DNA of human chromosome 1