英语高考复习 人教选修八 Unit 2 课文词汇语法填空 含答案

选修8 Unit 2 Cloning-Reading

CLONING: WHERE IS IT LEADING US?

Cloning has always been with us and is here to stay. It is a way of making an exact copy of another animal or plant. It happens in plants 1. gardeners take cuttings from growing plants to make new ones. It also happens in animals when twins identical in sex and appearance 2. (produce) from the same original egg. The fact is 3. these are both examples of natural clones.

Cloning has two major uses. Firstly, gardeners use it all the time to produce 3. ___________ (commence) quantities of plants. Secondly, it is valuable for research on new plant species and for medical research on animals. Cloning plants is straightforward while cloning animals is very complicated. It is a difficult task 4. ___________ (undertake). Many attempts to clone mammals failed. But at last the 5. ___________ (determine) and patience of the scientists paid 6. in 1996 with a ___________ (突破)- the cloning of Dolly the sheep. The procedure works like this: On the one hand, the whole 7. (science) world followed the progress of the first successful clone, Dolly the sheep. The fact that she seemed to develop normally was very 8. (encourage). Then came the disturbing news that Dolly 9. (become) seriously ill. Cloning scientists 10. (cast) down to find that Dolly's illnesses were more appropriate 11. a much older animal. Altogether Dolly lived six and a half years, half the 12. (long) of the life of the original sheep. 13. (sad) the same arbitrary fate affected other species, such as cloned mice. The questions that 14. (concern) all scientists were: "Would this be a major difficulty for all cloned animals? Would it happen forever? Could it 15. (solve) if corrections were made in their research procedure?"

On the other hand, Dolly's appearance raised a storm of 16. (object) and had a great impact on the media and public imagination. It became controversial. It suddenly opened everybody's eyes to 17. possibility of using cloning to cure serious illnesses and even 18. (produce) human beings.

Although at present human egg cells and embryos 19. (need) for cloning research are difficult to (获得), newspapers wrote of evil leaders hoping to clone themselves to ________ _________ ___________ (实现他们的野心). Religious leaders also raised (道德的) questions. Governments became nervous and more (保守的). Some began to reform their legal systems and 20. (forbid) research into human cloning, but other countries like China and the UK, continued to ___________ ___________ (积累证据) of the abundant medical aid that cloning could provide. However, scientists still wonder 21. ____________ cloning will help or harm us and where it is leading us.

THE RETURN OF THE DINOSAURS?

The possibility of cloning fierce and extinct wild animals has always excited film makers. And they are not the only ones! The 1. (popular) of films such as Jurassic Park, 2. which a scientist clones several kinds of extinct dinosaurs, proves how the idea 3. (strike) a mixture of fear and excitement 4. ________ people's hearts. But in fact we are a long way 5. being able to clone extinct animals. Scientists are still experimenting 6. cloning mammals. This is because the cloning of mammals is still a new science and its story only began seriously in the 1950s as this list shows:

1950s cloning of frogs 1996 first clone of a mammal: Dolly the sheep 1970s research using the embryos of mice 2000 cow gave birth to a bison

1979 work on embryos of sheep and mice 2001 China's first cloned twin calves 1981 first experimental clones of mice 2002 first cloned cats

1983 first experimental clones of cows 2005 first cloned dog

________ ________ _______ _______ (不时) people suggest that extinct animals like dinosaurs, can 7. (possible) be brought back to life through cloning. Unfortunately, with what we know now, this is either impossible or 8. _____________ (suit). There are many reasons.

◎The (最初的) requirement is that you need perfect DNA (which gives information for how cells are to grow).

◎All efforts of cloning an animal will be ______ _______ (徒劳) if there is not enough diversity in the group 9. (overcome) illnesses. Diversity in a group means 10. (have) animals with their genes arranged in different ways. The advantage is that 11. there is a new illness some of these animals may die, but others will survive and pass 12. the ability 13. (resist) that disease to the next generation. The great drawback to cloning a group of animals is that they would all have the same arrangement of genes and so might die of the same illness. Then none of them would 14. (leave) to continue the species. ◎It would be unfair to clone any extinct animals if they were to live in a zoo. A suitable habitat would be needed for them to lead a natural life.

15. (base) on what we know now, you cannot clone animals that have been extinct longer than 10,000 years. Actually, dinosaurs disappeared 65,000,000