★Don't wash those fossils!

Standard museum practice can wash away DNA.

1.    Washing, brushing and varnishing fossils — all standard conservation treatments used by many fossil hunters and museum curators alike — vastly reduces the chances of recovering ancient DNA.

2.    Instead, excavators should be handling at least some of their bounty with gloves, and freezing samples as they are found, dirt and all, concludes a paper in the Proceedings of the National Academy of Sciences today.

3.    Although many palaeontologists know anecdotally that this is the best way to up the odds of extracting good DNA, Eva-Maria Geigl of the Jacques Monod Institute in Paris, France, and her colleagues have now shown just how important conservation practices can be. This information, they say, needs to be hammered home among the people who are actually out in the field digging up bones.

4.    Geigl and her colleagues looked at 3,200-year-old fossil bones belonging to a single individual of an extinct cattle species, called an aurochs. The fossils were dug up at a site in France at two different times — either in 1947, and stored in a museum collection, or in 2004, and conserved in sterile conditions at -20 ºC.

5.    The team's attempts to extract DNA from the 1947 bones all failed. The newly excavated fossils, however, all yielded DNA.

6.    Because the bones had been buried for the same amount of time, and in the same conditions, the conservation method had to be to blame says Geigl. "As much DNA was degraded in these 57 years as in the 3,200 years before," she says.

Wash in, wash out

7.    Because many palaeontologists base their work on the shape of fossils alone, their methods of conservation are not designed to preserve DNA, Geigl explains.

8.    The biggest problem is how they are cleaned. Fossils are often washed together on-site in a large bath, which can allow water — and contaminants in the form of contemporary DNA — to permeate into the porous bones. "Not only is the authentic DNA getting washed out, but contamination is getting washed in," says Geigl.

9.    Most ancient DNA specialists know this already, says Hendrik Poinar, an evolutionary geneticist at McMaster University in Ontario, Canada. But that doesn't mean that best practice has become widespread among those who actually find the fossils.

10.  Getting hold of fossils that have been preserved with their DNA in mind relies on close relationships between lab-based geneticists and the excavators, says palaeogeneticist Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. And that only occurs in exceptional cases, he says.

11.  Pääbo's team, which has been sequencing Neanderthal DNA, continually faces these problems. "When you want to study ancient human and Neanderthal remains, there's a big issue of contamination with contemporary human DNA," he says.

12.  This doesn't mean that all museum specimens are fatally flawed, notes Pääbo. The Neanderthal fossils that were recently sequenced in his own lab, for example, had been part of a museum collection treated in the traditional way. But Pääbo is keen to see samples of fossils from every major find preserved in line with Geigl's recommendations — just in case.

Warm and wet

13.  Geigl herself believes that, with cooperation between bench and field researchers, preserving fossils properly could open up avenues of discovery that have long been assumed closed.

14.  Much human cultural development took place in temperate regions. DNA does not survive well in warm environments in the first place, and can vanish when fossils are washed and treated. For this reason, Geigl says, most ancient DNA studies have been done on permafrost samples, such as the woolly mammoth, or on remains sheltered from the elements in cold caves — including cave bear and Neanderthal fossils.

15.  Better conservation methods, and a focus on fresh fossils, could boost DNA extraction from more delicate specimens, says Geigl. And that could shed more light on the story of human evolution.

(640 words   nature )

Glossary

Palaeontologists    古生物学家

Aurochs 欧洲野牛

Neanderthal （人类学）尼安德特人，旧石器时代的古人类。

Permafrost     （地理）永冻层

Questions 1-6

Answer the following questions by using NO MORE THAN THREE WORDS for each answer.

1.        How did people traditionally treat fossils?

2.        What suggestions do Geigl and her colleagues give on what should be done when fossils are found?

3.        What problems may be posed if fossil bones are washed on-site? Name ONE.

4.        What characteristic do fossil bones have to make them susceptible to be contaminated with contemporary DNA when they are washed?

5.        What could be better understood when conservation treatments are improved?

6.        The passage mentioned several animal species studied by researchers. How many of them are mentioned?

Questions 7-11

Do the following statements agree with the information given in the passage? Please write

       TRUE                 if the statement agrees with the writer

       FALSE               if the statement does not agree with the writer

       NOT GIVEN      if there is no information about this in the passage

7.        In their paper published in the Proceedings of the National Academy of Sciences , Geigl and her colleagues have shown what conservation practices should be followed to preserve ancient DNA.

8.        The fossil bones that Geigl and her colleagues studied are all from the same aurochs.

9.        Geneticists don’t have to work on site.

10.    Only newly excavated fossil bones using new conservation methods suggested by Geigl and her colleagues contain ancient DNA.

11.    Paabo is still worried about the potential problems caused by treatments of fossils in traditional way.

Questions 12-13

Complete the following the statements by choosing letter A-D for each answer.

12.    “This information” in paragraph 3 indicates:

[A]  It is critical to follow proper practices in preserving ancient DNA.

[B]  The best way of getting good DNA is to handle fossils with gloves.

[C]  Fossil hunters should wear home-made hammers while digging up bones.

[D]  Many palaeontologists know how one should do in treating fossils.

13.  The study conducted by Geigl and her colleagues suggests:

[A]  the fact that ancient DNA can not be recovered from fossil bones excavated in the past.

       [B]  the correlation between the amount of burying time and that of the recovered

DNA.

       [C]  the pace at which DNA degrades.

       [D]  the correlation between conservation practices and degradation of DNA.

(by Zhou Hong)

Suggested answers and explanations

1.    washing, brushing, varnishing             见第一段。

2.    handling with gloves / freezing samples ( any one of the two )       见第二段。

3.    losing authentic DNA / being contaminated / contamination ( any one of the three)         见第八段“Not only is the authentic DNA getting washed out, but contamination is getting washed in”（答being contaminated或 contamination比较保险）

4.    they are porous            porous 的意思是多孔的。见第八段“... which can allow water — and contaminants in the form of contemporary DNA — to permeate into the porous bones.”

5.    human evolution           见第十五段。其中“shed light on sth”的意思是使某事显得非常清楚，使人了解某事。

6.    4     分别为第四段的“an extinct cattle species, called an aurochs”，即欧洲野牛，已经绝迹；第十一段“Neanderthal”， 是人类学用语，尼安德特人，旧石器时代的古人类；第十四段“woolly mammoth”和“cave bear”，其中mammoth是猛犸，一种古哺乳动物。

7.    T     见第二段。

8.    T     见第四段“Geigl and her colleagues looked at 3,200-year-old fossil bones belonging to a single individual of an extinct cattle species, called an aurochs.”即他们研究的骨化石是一头欧洲野牛身上的。

9.    NG

10.  F     见第十二段第一、二句话。

11.  T     见第十二段末句“But Pääbo is keen to see samples of fossils from every major find preserved in line with Geigl's recommendations — just in case.”意即为保险起见，Paabo还是非常希望见到用Geigl建议的方法保存的化石样本。“just in case” 的意思是以防万一，就是Paabo对用传统保存处理的化石不放心的意思。

12.  A    见第三段。This information就是前一句中“... just how important conservation practices can be”(to preserve good DNA)。“be hammered”之中hammer一词的意思是不断重复强调。

13.  D    面信息。需要理解文章各处关于Geigl和她的同事所作的研究。

 ★Search begins for 'Earth' beyond solar system

Staff and agencies

Wednesday December 27, 2006

Guardian Unlimited

1. A European spacecraft took off today to spearhead the search for another "Earth" among the stars.

2. The Corot space telescope blasted off aboard a Russian Soyuz rocket from the Baikonur cosmodrome in Kazakhstan shortly after 2.20pm.

3. Corot, short for convection rotation and planetary transits, is the first instrument capable of finding small rocky planets beyond the solar system. Any such planet situated in the right orbit stands a good chance of having liquid water on its surface, and quite possibly life, although a leading scientist involved in the project said it was unlikely to find "any little green men".

4. Developed by the French space agency, CNES, and partnered by the European Space Agency (ESA), Austria, Belgium, Germany, Brazil and Spain, Corot will monitor around 120,000 stars with its 27cm telescope from a polar orbit 514 miles above the Earth. Over two and a half years, it will focus on five to six different areas of the sky, measuring the brightness of about 10,000 stars every 512 seconds.

5. "At the present moment we are hoping to find out more about the nature of planets around stars which are potential habitats. We are looking at habitable planets, not inhabited planets. We are not going to find any little green men," Professor Ian Roxburgh, an ESA scientist who has been involved with Corot since its inception, told the BBC Radio 4 Today programme.

6. Prof Roxburgh said it was hoped Corot would find "rocky planets that could develop an atmosphere and, if they are the right distance from their parent star, they could have water".

7. To search for planets, the telescope will look for the dimming of starlight caused when an object passes in front of a star, known as a "transit". Although it will take more sophisticated space telescopes planned in the next 10 years to confirm the presence of an Earth-like planet with oxygen and liquid water, Corot will let scientists know where to point their lenses.

8. Measurements of minute changes in brightness will enable scientists to detect giant Jupiter-like gas planets as well as small rocky ones. It is the rocky planets - that could be no bigger than about twice the size of the Earth - which will cause the most excitement. Scientists expect to find between 10 and 40 of these smaller planets.

9. Corot will also probe into stellar interiors by studying the acoustic waves that ripple across the surface of stars, a technique called "asteroseismology".

10. The nature of the ripples allows astronomers to calculate a star's precise mass, age and chemical composition.

11. "A planet passing in front of a star can be detected by the fall in light from that star. Small oscillations of the star also produce changes in the light emitted, which reveal what the star is made of and how they are structured internally. This data will provide a major boost to our understanding of how stars form and evolve," Prof Roxburgh said.

12. Since the discovery in 1995 of the first "exoplanet" - a planet orbiting a star other than the Sun - more than 200 others have been found by ground-based observatories.

13. Until now the usual method of finding exoplanets has been to detect the "wobble" their gravity imparts on parent stars. But only giant gaseous planets bigger than Jupiter can be found this way, and they are unlikely to harbour life.

14. In the 2010s, ESA plans to launch Darwin, a fleet of four or five interlinked space telescopes that will not only spot small rocky planets, but analyse their atmospheres for signs of biological activity.

15. At around the same time, the US space agency, Nasa, will launch Terrestrial Planet Finder, another space telescope designed to locate Earth-like planets.

(615 words)

Choose the appropriate letter from A-D for question 1.

1.      Corot is an instrument which

(A) can help to search for certain planets

(B)   is used to find planets in the orbit

(C)   can locate planets with human beings

(D)   can spot any planets with water.

Do the following statements agree with the information given in the reading passage? For questions 2-5 write

TRUE                 if the statement agrees with the information

FALSE               if the statement contraicts the information

NOT GIVEN      if there is no information on this in the passage

2.      Scientists are trying to find out about the planets that can be inhabited.

3.      BBC Radio 4 recently focuses on the broadcasting of Corot.

4.      Passing objects might cause a fall in light.

5.      Corot can tell whether there is another Earth-like planet.

Based on your reading of the passage, complete the sentences below with

[1] [2] [3] 下一页