B
During the Ice Age, the mammoths (猛犸象) lived both in Asia and America. But by about 4,000 years ago, the large and hairy elephants had disappeared.
Some scientists want to clone a mammoth, and the first need is some mammoth DNA. Since 1900s, scientists have been digging up remains (残骸) of mammoths in the cold ground. Some still even have their skin and hair. Unluckily, even when it's frozen, DNA still can't be kept very well. It starts to break apart soon after an animal dies. Scientists have found plenty of mammoth DNA—but it's all just short bits and in a mess.
Modern Asian elephants are cousins of the ancient mammoths. Their DNA is about 99% the same. Still, that adds up to 70 million differences. But if we could change the elephant's DNA in the places that are different, could we make mammoth DNA? Some researchers at Harvard are giving it a try. They have got out 14 bits of DNA in elephant blood cells that help mammoths stand the cold. It seemed to work. But they're only working with groups of cells, not a whole animal. There is still a long way to go before cloning a mammoth.
Even if scientists could clone a mammoth or other disappeared animals, would it be a good idea? It might be cool to see a real, living mammoth. But would such an animal be happy, with no other mammoths around? Who would teach it how to be a mammoth? There are important questions for trying to bring back any disappeared creature. Cloning is expensive and often fails. Would the money be better spent in saving endangered animals that are still alive?
(
D
) 5. What happened to mammoth DNA?
A. It stayed the same. B. It got longer.
C. It disappeared. D. It broke apart.
(
C
) 6. What can we learn from the third paragraph?
A. The scientists are going to put the DNA of standing cold in another animal.
B. The scientists at Harvard have already cloned a mammoth very successfully.
C. It isn't easy to clone a disappeared animal though their DNA is close to some animals.
D. There are lots of differences of DNA between mammoths and modern Asian elephants.
(
C
) 7. Where can we most probably read this passage?
A. In a story magazine. B. In a cartoon newspaper.
C. On a science website. D. In a fashion report.
