VOA标准英语2009-Study Unlocks Genetic Diversity in Africa

A group of scientists has unveiled what they say is the most comprehensive study ever of African genes¹ which they say gives new insight into the origins of humans.

The genetic² study, a compilation³ of two big studies, confirms theories that modern humans evolved in Africa and then migrated through Europe and Asia to reach the Pacific and Americas. The study also shows that Africans have the most diverse DNA⁴, and the fewest potentially harmful genetic mutations.

Published in the US journal Science, researchers examined genetic material from 121 African populations, as well as four African-American populations and 60 non-African populations. The study aims to teach Africans on population history and aid research into why diseases hit particular groups.

The researchers found that after a population of humans migrated off the African continent, the group shrank for some unknown reason. Later populations grew and spread from this smaller genetic pool of ancestors.

Populations that remained in Africa kept their genetic diversity.

Sarah Tishkoff, a geneticist from the University of Pennsylvania, says the results provided insights about levels and patterns of genetic diversity in Africa. "That population had the highest levels of mixed ancestry⁵ on a global level. So, they had almost equal proportions of ancestry from Europeans. They also showed ancestry from East Asia, probably reflecting Southeast Asian ancestry, a little bit of Oceanic ancestry as well as south Indian ancestry," she said.

Widespread migrations⁶ also occurred on the continent itself, according to researchers who identified 14 ancestral population clusters who one time shared the same cultural characteristics and spoke⁷ the same languages.

The study of African diversity promises to provide valuable information in the field of biomedicine.

Scott Williams is a co-author of the study and a professor of biophysiology at Vanderbilt University in Tennessee. He says researchers will be able to trace diseases to certain Africa populations to help researchers understand their cause, with an eye toward developing treatments. "The examples that certainly I'm familiar with relate to diseases that are common in people of West African origin such as hypertension (and) prostate cancer. And some of these studies are ongoing⁸ in parts of West Africa," he said.

Tishoff says that the goal of the study is to benefit Africans, both by learning more about their population history and by setting the stage for future genetic studies, including studies of genetic and environmental risk factors for disease and drug response. "We don't want to see Africa populations get left behind in this genomic revolution. And so we hope this will stimulate⁹ further studies in Africa," she said.

The study also found that people of African descent are the most genetically¹⁰ diverse, followed by people from the Middle East, and then Asians and Europeans. Native Americans resemble one another the most on a DNA level.

1 genes   

n.基因( gene的名词复数 )

参考例句：

• 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

2 genetic   

adj.遗传的，遗传学的

参考例句：

• 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。

3 compilation   

n.编译，编辑

参考例句：

• One of the first steps taken was the compilation of a report.首先采取的步骤之一是写一份报告。
• The compilation of such diagrams,is of lasting value for astronomy.绘制这样的图对天文学有永恒的价值。

4 DNA   

(缩)deoxyribonucleic acid 脱氧核糖核酸

参考例句：

• 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。

5 ancestry   

n.祖先，家世

参考例句：

• Their ancestry settled the land in 1856.他们的祖辈1856年在这块土地上定居下来。
• He is an American of French ancestry.他是法国血统的美国人。

6 migrations   

n.迁移，移居( migration的名词复数 )

参考例句：

• It foundered during the turmoils accompanying the Great Migrations. 它在随着民族大迁徙而出现的混乱中崩溃。 来自辞典例句
• Birds also have built-in timepieces which send them off on fall and spring migrations. 鸟类也有天生的时间感应器指导它们秋春迁移。 来自互联网

7 spoke   

n.（车轮的）辐条；轮辐；破坏某人的计划；阻挠某人的行动 v.讲，谈（speak的过去式）；说；演说；从某种观点来说

参考例句：

• They sourced the spoke nuts from our company.他们的轮辐螺帽是从我们公司获得的。
• The spokes of a wheel are the bars that connect the outer ring to the centre.辐条是轮子上连接外圈与中心的条棒。

8 ongoing   

adj.进行中的，前进的

参考例句：

• The problem is ongoing.这个问题尚未解决。
• The issues raised in the report relate directly to Age Concern's ongoing work in this area.报告中提出的问题与“关心老人”组织在这方面正在做的工作有直接的关系。

9 stimulate   

vt.刺激，使兴奋；激励，使…振奋

参考例句：

• Your encouragement will stimulate me to further efforts.你的鼓励会激发我进一步努力。
• Success will stimulate the people for fresh efforts.成功能鼓舞人们去作新的努力。

10 genetically   

adv.遗传上

参考例句：

• All the bees in the colony are genetically related. 同一群体的蜜蜂都有亲缘关系。
• Genetically modified foods have already arrived on American dinner tables. 经基因改造加工过的食物已端上了美国人的餐桌。 来自英汉非文学 - 生命科学 - 基因与食物