Unit 2 Cloning
Ⅰ.阅读理解
A
The eventual extinction of the large prehistoric animals has always attracted researchers.However,it is impossible to recreate most of them,either because the fossilized (变成化石的) DNA is too old (dinosaur) or just not available.But the one exception may be the woolly mammoth,which lived about 8,000 years ago.
Thanks to their relatively recent disappearance and the ice-cold weather they lived in,plenty of well-preserved specimens (标本) have been discovered.In the last few years,scientists have been able to piece together the mammal’s genetic code(遗传密码)using some frozen hair and also recreate its blood,with the help of DNA that was found preserved in the bone.Now,a group of Japanese scientists want to take it one step further and bring the mammoth back to life.
The scientists of the team plan to start with a journey to Siberia this summer,to seek out the DNA from a flash-frozen specimen of the mammal.In case they are unable to find one,they will use the tissue of a preserved mammoth that currently sits in a Russian laboratory.
The scientists will join the mammoth’s DNA with an empty egg of the mammoth’s closest present-day relative—the elephant.Then,by using an electric current,they will trick the egg into growing and dividing.After a few days,the researchers will put it inside a female elephant,which will act as a surrogate mother (代孕母亲). Then begins the waiting game—for it takes about 600 days,for an elephant or in this case a woolly mammoth baby,to fully develop—that is,if everything goes well and the surrogate mother doesn’t reject the egg.
If luckily we do get a baby mammoth,scientists are not sure if they would produce more,but they are hoping they will be able to study it and answer the age-old question of how they became extinct—were they hunted down by humans or did they die because of climate change?
Will the woolly mammoth come back to life? We have to wait and see. 1.Why are the remains of the woolly mammoth kept well partly?
A.Due to their long hair. B.Due to their big size. C.Due to the coldness.
D.Due to human activity.
2.Why do the Japanese scientists plan to go to Siberia? A.To find suitable DNA. B.To preserve the specimen.
C.To recreate the mammoth’s blood. D.To seek help from the Russian scientists. 3.What does the fourth paragraph mainly talk about? A.The future of the cloned mammoth. B.The process of cloning the mammoth.
C.The difficulty the scientists are faced with. D.The relation between the mammoth and the elephant.
4.What are we most likely to do if the scientists’ efforts pay off? A.Clone a lot of mammoths.
B.Bring dinosaurs back to life.
C.Know the effects of climate change. D.Find out why the mammoth died out. 语篇解读:本文是说明文。日本的科学家正在尝试克隆猛犸象,企图复活这一史前庞然大物。 答案及剖析:
1.C 细节理解题。由第二段中的Thanks to...the ice-cold weather they lived in,plenty of well-preserved specimens(标本) have been discovered及frozen可知,猛犸象生活的地域气候寒冷,这使得它们的遗骸保存得比较完好。
2.A 细节理解题。由第三段中的to seek out the DNA from a flash-frozen specimen of the mammal可知,科学家去西伯利亚是要找到合适的猛犸象DNA。
3.B 段落大意题。由第四段中的join the mammoth’s DNA with an empty egg...Then,by using an electric current和After a few days可知,本段介绍了科学家克隆猛犸象将会实施的步骤。
4.D 细节理解题。由倒数第二段中的but they are hoping they will be able to study it and answer the age-old question of how they became extinct可知,如果克隆成功,科学家可以通过研究猛犸象宝宝来探究猛犸象灭绝的原因。
B
Researchers say they have created a new super-material in the laboratory.They say it is stronger,lighter and costs less than steel.
But the new material is not a product of high technology or a metallic
substance.It is wood.
Researchers Liangbing Hu and Teng Li are with the University of Maryland in the United States.
By using a few chemicals,heat and pressure,they have made wood three times denser and 10 times stronger.Hu says that means it can compete with some of the world’s strongest materials.
“We’re interested in replacing steel and carbon fibers with strong wood structures,” he said.
The process does not require any special raw,unprocessed material.Hu said that means the cost of the product will be relatively low.He added,“We can start with very cheap wood,and we can also start with very fancy,expensive wood.But in the end,ultimately we get very similar performance.”
The researchers are calling their product “super wood.” It is made by partially removing a natural polymer called lignin.
Hu explained that “lignin is like a binder to hold all the components together in natural wood.In our process,we found out to be able to densify the wood completely,we have to remove some of these binders.”
Strong chemicals are put on the wood.The chemicals remove about half of its lignin.Then,after being left in extreme heat and pressurized for a day,the treated wood is ready.The researchers say the wood is strong enough to build automobiles,airplanes,wind turbines and more.A report on their findings was published in the journal Nature.
The researchers say super-strength wood would have less of an effect on the environment than the steel or other metals it could replace.However,their process is not pollution-free.It uses some of the same chemicals involved in making paper.
Researcher Teng Li says he and Hu are finding many new ways to use wood,including creating batteries and see-through wood and paper.
“Wood has been existing on Earth more than a million years.And human beings have been using wood for furniture,construction for more than 10 thousand years.And the more we worked on this material,we realized,we have never fully exhausted the