题目内容
【题目】阅读下面文章,完成下题。
生命之剧的导演
郭礼和
“垃圾DNA”这个名字出自上世纪70年代。在这之前已经发现真核细胞(有细胞核结构的细胞)染色体上的基因之间是不连续的,也就是说,基因之间存在着很大的间隔,就像上海到北京的铁路有许多火车站,但这些火车站只占据铁路总长的1.5%(也就是基因只占DNA总长的1.5%)。故而,1972年美国加州理工学院大野乾把不编码蛋白的染色体片断称为“垃圾基因”。70年代后期,由于DNA测序技术的诞生和使用,证明不仅基因之间有很长的不编码DNA,就是基因内部也存在有许多不编码的间隔,说明一个完整的基因实际上是由许多不连续的DNA编码片断拼接起来的。因此,科学家把这些不编码蛋白信息的DNA统称为“垃圾DNA”。但是,对原核生物(没有细胞核的单细胞生物)DNA测序,发现它们的基因内部却是连续编码,基因之间的间隔也很短,说明它们的垃圾DNA很少。真核细胞与原核细胞的基因组和基因结构为什么有这样大的差异,这使人们产生很多联想和推测。
真核细胞产生这么多的“垃圾DNA”究竟干什么?到了上世纪80年代后期,DNA测序技术已经完全实现了自动化,故而人们提出将人类的基因组(人的细胞染色体全部DNA)序列进行分析,这就是所谓“人类基因组计划”。此计划从1990年启动到2003年完成,但是,这项人类历史上最大的科学工程实际上只是完成了一个草图。因为,研究人员只是将人类基因组的序列测出一部分,还有很多空隙未测出,主要是涉及到一些重复序列,它们的序列用现有技术很难测出。根据已测出的序列和结构分析,基因只有2.6万个左右,占基因组总长度约1.5%,而98.5%的DNA为非编码区,也就是人们通常所说的“垃圾DNA”。这98.5%的“垃圾DNA”究竟有什么用处?于是,科学家们在完成“人类基因组计划”的草图之后,启动了ENCODE研究计划,进一步对那些基因组空白处进行测序,并探索这些大量的“垃圾DNA”的功能,编篡DNA元件百科全书。上述两个研究计划可以分别称为“结构基因组计划”和“功能基因组计划”。
“结构基因组计划”的完成证明:人类和小鼠的基因组大小、基因种类和数量、甚至基因的结构都很相似,但在个体形态和智慧方面的差异却有天壤之别。他们的基因组最大的差异就是“垃圾DNA”,由此可见“垃圾DNA”并不“垃圾”,它可能与物种进化、胚胎发育、个体生长、疾病发生、机体衰老和死亡等生命现象都有着密切关系,也就是与控制基因的变异、突变、表达、调控等密切相关。
可以把生命活动简单地理解为一台电脑在进行一项工程设计,例如用电脑设计飞机。要完成这项任务需要两样东西,一个是“数据库”,另一个是“软件包”。有了这两项工具就可以设计出个各种类型的飞机。生命活动中的基因库可以把它理解为“数据库”,因为小鼠、猴子与人类的基因库大同小异,而且可以相互替代。“垃圾DNA”可以把它理解为“软件包”,利用不同物种的“软件包”(也就是不同物种的“垃圾DNA”)可以设计出小鼠、猴子或人的有机体。
可以把生命活动理解为拍一部电影,基因组就是电影的剧本,基因编码的蛋白质可以理解为演员,“垃圾DNA”就是导演。不同演员的出场和退场或再次出场都是导演根据剧本的情节来安排,这样就可以展现出一部有血有肉有情感的动人场面。导演不仅要指导演员的表演,而且要安排舞台灯光变幻和道具的变化来烘托舞台场景和故事情节。“垃圾DNA”在生命活动中的演绎也是像电影导演那样如此忙碌,故而需要大量的“垃圾DNA”,但它们不出场,也就是不编码蛋白在细胞的生命活动舞台上出现,可是不同蛋白何时出场何时退场或再出场却是由“垃圾DNA”来决定的。
从某种意义上来说,物种相近的基因组主要差异不在基因(当然基因也可有差异),而是“垃圾DNA”。例如,人和猴子;尤其人与人之间的遗传差异主要是“垃圾DNA”,这就造成人与人对疾病的发生和药物敏感性有差异,也就是为什么需要个体化医疗的原因。
(有删节 )
(1)作者认为“垃圾DNA”有哪些方面的作用?
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(2)这篇科普文的语言形象生动,请指出其手法,并举两例简要说明。
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(3)请谈谈你对本文标题的理解。
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【答案】(1)①“垃圾DNA”设计出不同物种的生命体,使基因组大小、基因种类和数量、甚至基因的结构都很相似的人类和小鼠,在个体形态和智慧方面的差异有天壤之别。②“垃圾DNA”决定不同蛋白的出场时间、次序,控制基因的变异、突变、表达、调控等,导致不同物种、甚至是同一物种间出现遗传差异。
(2)运用比喻的手法生动地说明事物特性。如第一段将基因比作北京到上海之间铁路上的火车站,把“垃圾DNA”比作各火车站之间的铁路,生动形象地说明了真核细胞染色体上的基因与“垃圾DNA”各自所占的比例。第五段将“垃圾DNA”比作“导演”形象生动地说明了其在控制基因变异、突变等方面的作用。
(3)①标题中生命之剧的导演指的是被称为“垃圾DNA”的不编码蛋白信息DNA,它像导演指导一部电影一样,主导着生命活动的遗传差异和个体特征,让生命的形态各异。形象地说明了“垃圾DNA”在“生命之剧”中所起到的关键性作用。②这个标题具有科普文标题的一般特点,通俗生动,可以让读者产生阅读的兴趣。
【解析】略
【题目】
Teamwork is just as important in science as it is on the playing field or in the gym. Scientific investigations(调查) are almost always carried out by teams of people working together. Ideas are shared, experiments are designed, data are analyzed, and results are evaluated and shared with other investigators. Group work is necessary, and is usually more productive than working alone.
Several times throughout the year you may be asked to work with one or more of your classmates. Whatever the task your group is assigned, a few rules need to be followed to ensure a productive and successful experience.
What comes first is to keep an open mind, because everyone’s ideas deserve consideration and each group member can make his or her own contribution. Secondly, it makes a job easier to divide the group task among all group members. Choose a role on the team that is best suited to your particular strengths. Thirdly, always work together, take turns, and encourage each other by listening, clarifying, and trusting one another. Mutual support and trust often make a great difference.
Activities like investigations are most effective when done by small groups. Here are some more suggestions for effective team performance during these activities: Make sure each group member understands and agrees to the task given to him or her, and everyone knows exactly when, why and what to do take turns doing various tasks during similar and repeated activities; be aware of where other group members are and what they are doing so as to ensure safety; be responsible for your own learning, though it is by no means unwise to compare your observations with those of other group members.
When there is research to be done, divide the topic into several areas, and this can explore the issue in a very detailed way. You are encouraged to keep records of the sources used by each person, which helps you trace back to the origin of the problems that may happen unexpectedly. A format for exchanging information (e.g., photocopies of notes, oral discussion, etc.) is also important, for a well-chosen method not only strengthens what you present but also makes yourself easily understood. When the time comes to make a decision and take a position on an issue, allow for the contributions of each member of the group. Most important of all, it is always wise to make decisions by compromise and agreement.
After you’ve completed a task with your team, make an evaluation of the team’s effectiveness---the strengths and weaknesses, opportunities and challenges.
根据短文内容完成下列表格,一空一词。
Title | Working Together |
Theme | Effective performance needs highly cooperated 【1】 . |
General rules | ·Keep an open mind to everyone’s 【2】 . ·Divide the group task among group members. ·【3】 and trust each other. |
【4】 | ·Understand and agree to the 【5】 task of one’s own. ·Take turns doing various tasks. ·Show concern for others to ensure safety. ·Take 【6】 for one’s own learning. ·Compare your own observations with those of others. |
Explore an issue | ·Break the 【7】 into several areas. ·Keep records of the sources just in 【8】 . ·【9】 your information with others via proper format. ·Make all decisions by compromise and agreement. |
【10】 effectiveness | ·Analyze the strengths and weaknesses. ·Find out the opportunities and challenges. |