(单词翻译:单击)
听力文本
This is PEOPLE IN AMERICA in VOA Special English. Today, Jim Tedder and Shirley Griffith tell about Barbara McClintock. She was one of the most important scientists of the twentieth century. She made important discoveries about genes and chromosomes.
Barbara McClintock was born in nineteen-oh-two in Hartford, Connecticut. Barbara was the third of four children. Her family moved to the Brooklyn area of New York City in nineteen-oh-eight. Barbara was an active child with interests in sports and music. She also developed an interest in science.
She studied science at Cornell University in Ithaca, New York. Barbara was among a small number of undergraduate students to receive training in genetics in nineteen twenty-one. Years later, she noted that few college students wanted to study genetics.
In the early nineteen twenties, genetics had not received widespread acceptance as a subject. Only twenty years had passed since scientists rediscovered the theories of heredity. Austrian researcher Gregor Mendel had proposed these ideas in the middle of the nineteenth century after completing a series of experiments with plants. His work helped scientists better understand how genes operate. They showed how genetic qualities are passed to living things from their ancestors.
Barbara McClintock decided to study botany, the scientific study of plants, at Cornell University. She completed her undergraduate studies in nineteen twenty-three. McClintock decided to continue her education at Cornell. She completed a master's degree in nineteen twenty-five. Two years later, she finished all her requirements for a doctorate degree.
In the late nineteen twenties, McClintock joined several other students in a group that studied genetics. The students included a future winner of the Nobel Prize, George Beadle. Another was Marcus Rhoades. Years later, he would become a leading expert in genetics.
McClintock said both men recognized the importance of exploring the connection between genes and chromosomes.
McClintock stayed at Cornell after she completed her education. She taught students botany. She also supervised genetic studies of the corn plant, or maize. She studied chromosomes, which are lines of genes. She made several discoveries about genes and chromosomes.
The nineteen thirties were not a good time to be a young scientist in the United States. The country was in the middle of the great economic Depression. Millions of Americans were unemployed. Male scientists were offered jobs. But female geneticists were not much in demand.
McClintock received two offers to travel and carry out research projects. The first came from America's National Research Council. She worked at several places, including Cornell and the University of Missouri in Columbia. Later, a group called the Guggenheim Foundation provided financial aid for her to study in Germany. McClintock went to Berlin, but returned to Cornell the following year. Her skills and work were widely praised. But she still was unable to find a permanent job.
For years, scientists had been using x-rays to study genetic material in plants and other organisms. They found that x-rays caused genes to change.
Sometimes, the x-rays physically broke the chromosome. Genetic researchers looked for changes in the organism. Then they used this information to produce a map linking the changes to a single area of the chromosome.
McClintock became interested in the way genes reacted to unusual events. She formed a successful working relationship with Lewis Stadler of the University of Missouri. He had demonstrated the effects of x-rays on corn.
Stadler sent maize treated with radiation to McClintock. She identified unusual areas she called ring chromosomes. She believed they were chromosomes broken by radiation. The broken ends sometimes joined together and formed a circle, or ring. This led her to believe that a structure at the end of the chromosome prevents chromosomes from changing. She called this structure the telomere.
Stadler got the University of Missouri to offer a permanent position to McClintock in nineteen thirty-six. She became an assistant professor.
During her time at the university, she worked with plants treated with x-rays. She also discovered plants with chromosomes that broke without help of radiation. She described this activity as the breakage-fusion-bridge cycle.
University officials and professors recognized the importance of McClintock's research. Yet she believed that she was not able to make progress in her position. So she decided to leave the University of Missouri.
An old friend from Cornell, Marcus Rhoades, invited McClintock to spend the summer of nineteen forty-one working at the Cold Spring Harbor Laboratory. It is a research center on Long Island, near New York City.
McClintock started in a temporary job with the genetics department. A short time later, she accepted a permanent position with the laboratory. This gave her the freedom to continue her research without having to teach or repeatedly ask for financial aid.
At Cold Spring Harbor Laboratory, McClintock continued her work with the breakage-fusion-bridge cycle. She found that some corn plant genes acted in an unusual way. They appeared to move from cell to cell during development of corn particles, or kernels. She discovered that the genes moved on and between chromosomes.
McClintock confirmed her discovery and extended her observations for six years. The changes could not be explained by any known theory. So, she developed her own theory. She believed the moveable genes were not genes at all, but genetic controllers or controlling elements. She said they influenced the actions of other genes.
During this period, McClintock was elected to the National Academy of Sciences. She was the third woman ever so honored. She also was named president of the Genetics Society of America.
In nineteen fifty-one, McClintock was asked to present her findings at a conference held at Cold Spring Harbor Laboratory. Her report described the movement of genes from one part of a chromosome to another. She used the presentation to discuss her ideas of controlling elements in genes.
The other scientists reacted to her ideas with a mixture of criticism and silence. Most scientists believed that genes did not move. Few people seemed to accept her findings. Yet others argued that her experiments were complex and difficult to explain, even to other scientists. They said she would not have been invited to speak unless conference organizers understood some of the importance of her work.
For years, many scientists dismissed McClintock's findings. During this period, she continued doing her own work and reaching her own findings.
Beginning in the late nineteen fifties, she went to Central and South America to study different kinds of maize plants. She examined the development of agricultural maize by native peoples. She also assisted younger scientists and students in genetics.
Her work at the Cold Spring Harbor Laboratory was recognized in nineteen seventy. She was given the American government's highest science award – the National Medal of Science.
By the nineteen seventies, newly developed methods of molecular biology confirmed what McClintock had learned through observation. Her discoveries have had an effect on everything from genetic engineering to cancer research.
McClintock won the Nobel Prize for Physiology or Medicine in nineteen eighty-three for her discovery of the ability of genes to change positions on chromosomes. She was the first American woman to win an unshared Nobel Prize.
Barbara McClintock remained at Cold Spring Harbor for the rest of her life. She died in nineteen ninety-two. She was ninety years old.
重点解析
1.develop an interest in培养一种兴趣
How did you happen to develop an interest in French poetry?
你怎么偏偏对法国诗歌感兴趣？
2.carry out执行；实行
They will carry out this experimentation, regardless of what happen.
不管发生什么，他们都将完成这个实验。
3.at the end of在……尽头；
We are at the end of an era, not only in Europe, but globally.
我们来到了一个时代的终结点，不仅对欧洲如此，对全球也是如此。
4.react to作出反应；
Some of these sensors react to physical phenomena such as light, temperature, and so on.
在这些传感器中，有些对诸如光亮、温度等物理现象作出反应。
5.have an effect on对…有影响
The ambassador said that de facto sanctions already are beginning to have an effect on Iran.
舒尔特说，对伊朗实际上的制裁已开始对伊朗产生影响。
6.make progress取得进展
And in the coming weeks and months, I hope that we can work together, Democrats and Republicans and Independents alike, to make progress on these and other issues.
而在今后几周和几个月里，我希望我们能够共同努力，不论民主党人、共和党人和无党派人士一样，在各类事务上取得进展。
参考译文
这里是VOA慢速英语栏目《美国人物志》。今天，吉姆·特德和雪莉·格里菲斯为您讲述芭芭拉·麦克林托克的故事。她是20世纪最重要的科学家之一。芭芭拉在基因和染色体方面有重大发现。
芭芭拉·麦克林托克于1902年出生在康涅狄格州的哈特福德市。芭芭拉是四个孩子中的第三个。1908年，她的家人搬到了纽约市的布鲁克林地区。芭芭拉是个对运动和音乐有兴趣的活泼的孩子。她也对科学产生了兴趣。
她曾在纽约州伊萨卡市的康奈尔大学学习科学。芭芭拉是在1921年接受遗传学培训的少数本科生之一。多年以后，她发现有很少的学生想学习遗传学。
在20世纪20年代早期，遗传学作为一门学科没有得到广泛的接受。自从科学家重新发现了遗传学理论以来，仅仅才过去了20年。19世纪中叶，奥地利科学家格里格·孟德尔在完成一系列植物实验后提出了这些想法。他的工作帮助科学家们更好地理解基因是如何运作的。他们展示了基因品质是如何从祖先遗传给后代的。
芭芭拉·麦克林托克决定在康奈尔大学学习植物学，这是一门关于植物的科学研究。她在1923年完成了本科学业。麦克林托克决定继续在康奈尔大学深造。她在1925年完成了硕士学位。两年后，她满足了取得博士学位的所有要求。
在20世纪20年代晚期，麦克林托克和其他几个学生加入了一个学习遗传学的小组。这些学生中包括一名未来的诺贝尔奖得主，乔治·比德尔。另外一个学生是马库斯·罗迪斯。几年后，他将成为一名遗传学领域的顶尖专家。
麦克林托克说，他们两个人都认同探索基因和染色体之间的关系的重要性。
麦克林托克在完成自己的学业后留在了康奈尔大学。她教授植物学课程。她还指导了有关玉米的基因研究。她研究染色体，也就是基因序列。她在基因和染色体方面有了一些发现。
在美国，20世纪30年代对于一个年轻的科学家来说不是一个好时期。这个国家正处于经济大萧条时期。数百万美国人失业。男性科学家得到了工作机会。但女性遗传学家的需求量并不大。
麦克林托克收到了两份旅行和调研项目的工作邀请。第一个来自美国国家研究委员会。她在好几个地方工作过，包括康奈尔大学和哥伦比亚的密苏里大学。后来，一个名为古根海姆基金会的组织为她在德国学习提供了经济援助。麦克林托克去了柏林，但第二年她又回到了康奈尔。她的技艺和工作得到了广泛赞誉。但是她仍然不能找到一份长久的工作。
多年来，科学家们一直在利用x射线研究植物和其他生物的遗传物质。他们发现x射线会导致基因改变。
有时候，x射线会破坏染色体。基因研究人员研究有机体的变化。然后他们利用这些信息制作了一个地图，将这些变化和染色体的单个区域联系起来。
麦克林托克开始对基因对不寻常事件的反应方式感兴趣。她与密苏里大学的刘易斯·施塔德勒建立了成功的工作关系。他已经证明了x射线对玉米的影响。
施塔特勒把经过辐射处理的玉米送给麦克林托克。她发现了一些不寻常的区域，她称之为环状染色体。她认为环状染色体就是遭到辐射破坏的染色体。被破坏的染色体末端有时候会连在一起，形成一个环。这个发现让她相信染色体末端的某个结构会阻止染色体发生变化。她称这种结构为端粒。
1936年，斯塔德勒让密苏里大学给麦克林托克提供了一个长久的职位。她成为了一名助理教授。
麦克林托克在这所大学的时候，她研究x射线处理过的植物。她也发现了染色体未经x射线照射而被破坏的植物。她把这种活动称为“断裂-融合-桥梁循环”。大学官员和教授认可了麦克林托克研究的重要性。但是她认为自己在现在的职位上不能取得进步。所以她离开了密苏里大学。
1941年夏天，一位来自康奈尔的老友马库斯·罗迪斯邀请麦克林托克去冷泉港实验室工作。它是位于纽约附近的长岛的一个研究中心。
麦克林托克开始在那里的遗传学部门临时工作。不长一段时间后，她就接受了该实验室的一个永久职位。这样，她就有了继续做自己研究的自由，而不用去教学或经常地寻求经济援助。
在冷泉港实验室，麦克林托克继续她的断裂-融合-桥梁循环的工作。她发现一些玉米植物的基因以一种不寻常的方式起着作用。在玉米粒生长的过程中，这些基因似乎不断地在细胞间移动。她发现基因在染色体之间移动。
麦克林托克证实了她的发现，并将观察时间延长了6年。这些变化无法用任何已知的理论来解释。因此，她发展了自己的理论。她认为这些可移动的基因根本不是基因，而是基因控制者或控制元素。她说它们影响其他基因的行为。
在此期间，麦克林托克当选为美国国家科学院院士。她是第三位获得如此殊荣的女性。她还被任命为美国遗传学学会主席。
1951年，麦克林托克受邀请在冷泉港实验室举行的会议上展示她的发现。她的报告描述了基因从染色体的一个部分到另一个部分的运动。她利用这次演讲讨论了她关于基因中控制元素的想法。
其他科学家对她的想法的反应是批评或沉默。大多数科学家认为基因是不会移动的。似乎又很少人接受她的发现。但是其他人认为她的实验是复杂的和难以解释的，即使对科学家来说也是一样。他们说，除非会议的组织者明白麦克林托克工作的一些重要性，否则她是不会受邀去做演讲的。
多年来，许多科学家对麦克林托克的发现不屑一顾。在此期间，她继续自己的研究，并取得了自己的发现。
从20世纪50年代末开始，她前往中美洲和南美洲研究不同种类的玉米作物。她研究了当地居民种植玉米的发展情况。她还在遗传学方面帮助年轻的科学家和学生。
她在冷泉港实验室的研究成果在20世纪70年代得到了认可。她获得了美国政府的最高科学奖项-美国国家科学奖。
到20世纪70年代，分子生物学新发展的方法确认了麦克林托克通过观察得来的发现。她的发现影响了从基因工程到癌症研究的方方面面。
1983年，麦克林托克因发现基因改变染色体位置的能力而获得诺贝尔生理学或医学奖。她是第一位独自获得诺贝尔奖的美国女性。
芭芭拉·麦克林托克在冷泉港度过了余生。她于1992年逝世。享年九十岁。
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