新视野大学英语 读写教程第四册 unit7-a
时间:2018-12-29 作者:英语课 分类:新视野大学英语读写教程(4)
Research into Population Genetics
While not exactly a top selling book, The History and Geography of Human Genes 2 is a remarkable 3 collection of more than 50 years of research in population genetics. It stands as the most extensive survey to date on how humans vary at the level of their genes. The book's firm conclusion: once the genes for surface features such as skin color and height are discounted, the "races" are remarkably 4 alike under the skin. The variation among individuals is much greater than the differences among groups. In fact, there is no scientific basis for theories pushing the genetic 1 superiority of any one population over another.
The book, however, is much more than an argument against the latest racially biased 5 theory. The prime mover behind the project, Luca Cavalli-Sforza, a Stanford professor, labored 6 with his colleagues for 16 years to create nothing less than the first genetic map of the world. The book features more than 500 maps that show areas of genetic similarity — much as places of equal altitude are shown by the same color on other maps. By measuring how closely current populations are related, the authors trace the routes by which early humans migrated around the earth. Result: the closest thing we have to a global family tree.
The information needed to draw that tree is found in human blood: various proteins that serve as markers to reveal a person's genetic makeup 7. Using data collected by scientists over decades, the authors assembled profiles of hundreds of thousands of individuals from almost 2,000 groups. And to ensure the populations were "pure", the study was confined to groups that were in their present locations as of 1492, before the first major movements from Europe began — in effect, a genetic photo of the world when Columbus sailed for America.
Collecting blood, particularly from ancient populations in remote areas, was not always easy; potential donors 8 were often afraid to cooperate, or raised religious concerns. On one occasion, when Cavalli-Sforza was taking blood samples from children in a rural region of Africa, he was confronted by an angry farmer waving an axe 9. Recalls the scientist: "I remember him saying, ’If you take the blood of the children, I'll take yours.’ He was worried that we might want to do some magic with the blood."
Despite the difficulties, the scientists made some remarkable discoveries. One of them jumps right off the book's cover: a color map of the world's genetic variation has Africa at one end of the range and Australia at the other. Because Australia's native people and black Africans share such superficial characteristics as skin color and body shape, they were widely assumed to be closely related. But their genes tell a different story. Of all humans, Australians are most distant from the Africans and most closely resemble their neighbors, the Southeast Asians. What the eye sees as racial differences — between Europeans and Africans, for example — are mainly a way to adapt to climate as humans move from one continent to another.
The same map, in combination with ancient human bones, confirms that Africa was the birthplace of humanity and thus the starting point of the original human movements. Those findings, plus the great genetic distance between present-day Africans and non-Africans, indicate that the split from the African branch is the oldest on the human family tree.
The genetic maps also shed new light on the origins of populations that have long puzzled scientists. Example: the Khoisan people of southern Africa. Many scientists consider the Khoisan a distinct race of very ancient origin. The unique character of the clicking sounds in their language has persuaded some researchers that the Khoisan people are directly descended 10 from the most primitive 11 human ancestors. But their genes beg to differ. They show that the Khoisan may be a very ancient mix of west Asians and black Africans. A genetic trail visible on the maps shows that the breeding ground for this mixed population probably lies in Ethiopia or the Middle East.
The most distinctive 12 members of the European branch of the human tree are the Basques of France and Spain. They show unusual patterns for several genes, including the highest rate of a rare blood type. Their language is of unknown origin and cannot be placed within any standard classification. And the fact that they live in a region next to famous caves which contain vivid paintings from Europe's early humans, leads Cavalli-Sforza to the following conclusion: "The Basques are extremely likely to be the most direct relatives of the Cro-Magnon people, among the first modern humans in Europe." All Europeans are thought to be a mixed population, with 65% Asian and 35% African genes.
In addition to telling us about our origins, genetic information is also the latest raw material of the medical industry, which hopes to use human DNA 13 to build specialized 14 proteins that may have some value as disease-fighting drugs. Activists 15 for native populations fear that the scientists could exploit these peoples: genetic material taken from blood samples could be used for commercial purposes without adequate payment made to the groups that provide the DNA.
Cavalli-Sforza stresses that his mission is not just scientific but social as well. The study's ultimate aim, he says, is to "weaken conventional notions of race" that cause racial prejudice. It is a goal that he hopes will be welcomed among native peoples who have long struggled for the same end.
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- It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
- Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。
- You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因,所以能够活得很长。 来自《简明英汉词典》
- Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪
- She has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
- These cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。
- I thought she was remarkably restrained in the circumstances. 我认为她在那种情况下非常克制。
- He made a remarkably swift recovery. 他康复得相当快。
- a school biased towards music and art 一所偏重音乐和艺术的学校
- The Methods: They employed were heavily biased in the gentry's favour. 他们采用的方法严重偏袒中上阶级。
- I was close enough to the elk to hear its labored breathing. 我离那头麋鹿非常近,能听见它吃力的呼吸声。 来自辞典例句
- They have labored to complete the job. 他们努力完成这一工作。 来自辞典例句
- Those who failed the exam take a makeup exam.这次考试不及格的人必须参加补考。
- Do you think her beauty could makeup for her stupidity?你认为她的美丽能弥补她的愚蠢吗?
- Please email us to be removed from our active list of blood donors. 假如你想把自己的名字从献血联系人名单中删去,请给我们发电子邮件。
- About half this amount comes from individual donors and bequests. 这笔钱大约有一半来自个人捐赠及遗赠。 来自《简明英汉词典》
- Be careful with that sharp axe.那把斧子很锋利,你要当心。
- The edge of this axe has turned.这把斧子卷了刃了。
- A mood of melancholy descended on us. 一种悲伤的情绪袭上我们的心头。
- The path descended the hill in a series of zigzags. 小路呈连续的之字形顺着山坡蜿蜒而下。
- It is a primitive instinct to flee a place of danger.逃离危险的地方是一种原始本能。
- His book describes the march of the civilization of a primitive society.他的著作描述了一个原始社会的开化过程。
- She has a very distinctive way of walking.她走路的样子与别人很不相同。
- This bird has several distinctive features.这个鸟具有几种突出的特征。
- DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
- Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。
- There are many specialized agencies in the United Nations.联合国有许多专门机构。
- These tools are very specialized.这些是专用工具。