题目内容
7.Blue-eyed people have been living in Europe for at least 7,000years,scientists have discovered.A man who lived on the Iberian Peninsula before Europeans became farmers probably had blue eyes but dark hair and skin,according to scientists who have sequenced (排序) his DNA.This surprising combination of eye,hair and skin coloring may not have been unusual during his lifetime,but it is no longer seen among modern Europeans,the team reported Sunday in the journal Nature.
The man,a Neolithic hunter-gatherer known to scientists as La Bra?a 1,is of great interest to scientists because he offers a photograph of what was in Europeans'DNA before agriculture (农业) spread through the continent.Experts have understood that certain genetic (基因的) features spread quickly among humans after they led the farming lifestyle.La Bra?a 1shows that at least some of their expectations were correct.
The man's skeleton,along with that of a male companion,was discovered in 2006in a cave in what is now northeastern Spain.The site,known as La Bra?a-Arintero,sits about 5,000feet above sea level,and the cave provided a cold,refrigerator-like environment that preserved his DNA.
In the lab,scientists were able to take out enough DNA from a single tooth to reconstruct La Bra?a 1's entire genome (基因组).They compared it to the DNA of other ancient Europeans and determined that he was a closer match with hunter-gatherers than with farmers.
When it came to genes that would influence La Bra?a 1's appearance,the researchers found that their 7,000-year-old subject had versions of two skin pigment (色素) genes that are either very rare or nonexistent among Europeans today.Then they looked at other places in the genome that influence pigmentation and found a mix of ancient and modern gene variants (变体).Taken together,La Bra?a 1's DNA"is likely to have resulted in dark skin pigmentation and dark or brown hair,"they wrote.
However,his DNA indicates that his eyes were most likely blue,the scientists found.This suggests that gene variants for light-colored eyes and skin did not spread together,they wrote,adding that La Bra?a 1's combination"of dark skin and non-brown eyes is unique and no longer present in contemporary European populations."Today,a blue-eyed person would usually have fair skin.
To get some idea of whether La Bra?a 1's coloring was unusual for his day,the researchers will try to sequence the DNA of his companion,who has been named La Bra?a=2.
25.Why scientists are interested in La Bra?a 1?B
A.They can know Europeans'DNA.
B.They can know European hunter-gatherers'DNA.
C.They can know the ancient agriculture in Europe.
D.They can know some of their expectations were correct.
26.La Bra?a 1was well preserved due toD.
A.dry weather
B.a high cave
C.proper protection
D.cold conditions
27.Which of the following is TRUE according to the passage?A
A.La Bra?a 1's DNA influenced his appearance.
B.La Bra?a 1's appearance influenced contemporary Europeans.
C.La Bra?a 1's gene variants spread together.
D.La Bra?a 1's genes are completely different from contemporary Europeans'.
28.The last paragraph suggests thatD.
A.La Bra?a 2has the same genome with La Bra?a 1
B.Blue-eyed people were common in Europe 7,000years ago
C.Bra?a 1's combination of dark skin and non-brown eyes is unique
D.It's not certain that La Bra?a's appearance was common at his time.
分析 本文属于说明文阅读,作者通过这篇文章主要向我们介绍了最近关于 La BranaⅠ的调查,事实证明这个群体的基因已经存在了七千多年,但是这个基因并没有广泛存在,蓝眼睛的人在欧洲依然很少.
解答 BDAD
25.B 细节理解题,根据第三段The man,a Neolithic hunter-gatherer known to scientists as La BranaⅠ,is of great interest to scientists because he offers a brief introduction to what was in Europeans'DNA before agriculture spread through the continent.可知科学家们研究 La BranaⅠ是因为他们想知道欧洲猎人的DNA,故选B.
26.D 细节理解题题,根据第四段The site,known as La Brana-Arintero,sits about 5,000feet above sea level,and the cave provided a cold,refrigerator-like environment that preserved his DNA.可知La BranaⅠ的骨架保存最好的主要原因是因为洞里的寒冷条件,故选D.
27.A 推理判断题,根据第六段Taken together,La BranaⅠ's DNA"is likely to have resulted in dark skin pigmentation and dark or brown hair,"they wrote.可知La BranaⅠ的基因可能导致黑皮肤色素沉着,以及黑色或棕色的头发,因此可推断出它能影响人们的外表,故选A.
28.D 推理判断题,根据最后一段This suggests that gene variants for light-colored eyes and skin did not spread together,they wrote,adding that La BranaⅠ's combination"of dark skin and non-brown eyes is unique and no longer present in contemporary European populations."Today,a blue-eyed person would typically have fair skin.可知La Brana的外表并不是常见的,故选D.
点评 阅读理解题测试考生在阅读基础上的逻辑推理能力,要求考生根据文章所述事件的逻辑关系,对未说明的趋势或结局作出合理的推断;或根据作者所阐述的观点理论,对文章未涉及的现象、事例给以解释.考生首先要仔细阅读短文,完整了解信息,准确把握作者观点.