original sheep. Sadly the same arbitrary fate affected other species, such as cloned mice. The questions that concerned all scientists were: \cloned animals? Would it happen forever? Could it be solved if corrections were made in their research procedure?\

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

Although at present human egg cells and embryos needed for cloning research are difficult to obtain, newspapers wrote of evil leaders hoping to clone themselves to attain their ambitions. Religious leaders also raised moral questions. Governments became nervous and more conservative. Some began to reform their legal systems and forbade research into human cloning, but other countries like China and the UK, continued to accumulate evidence of the abundant medical aid that cloning could provide. However, scientists still wonder whether cloning will help or harm us and where it is leading us.

克隆一直在我们左右并且已经被大多数人接受。它是一种用来准确复制其他动物或者植物的方法。在植物方面,克隆就发生在园丁从正在生长的植物上切去切口用来制造新的植株的时候。在动物方面也有克隆现象,比如说两个拥有同样性别以及外貌的同卵双胞胎。这两个事实都是自然界里的克隆例子。

克隆有2方面的主要用途。首先,园丁可以一直用它生产具有商业价值的植物。其次,它对于新的植物物种以及动物医药方面的研究极具价值性。植物克隆相对于动物克隆来说简单得多,而动物克隆则比较困难。

动物克隆是一项难以施行的任务。许多去克隆哺乳动物的尝试都以失败告终。但是在最后,科学家们凭借着决心和耐心终于在1996年取得了突破性的成功——成功地克隆出了多利羊。这项工作的步骤如下:

1.从母羊A体内取出卵细胞。 2.将细胞核从该卵细胞中移除。 3.该卵细胞为另一个新的细胞核准备。

4.从母羊B体内取出体细胞用于克隆。该体细胞内的细胞核包含了克隆一只新的羊所需的全部基因。

5.将该细胞核从体细胞中取出。

6.用电激的方法将从母羊B体内取出的细胞核与从母羊A体内取出的卵细胞融合。

7.重新融合的细胞在胚胎内分裂、生长。

8.将胚胎植入母羊C的体内,它将成为该克隆的携带者。

9.克隆出来的小羊羔体内细胞的基因来自于提供细胞核的母羊B。 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 popularity of films such as Jurassic Park, in which a scientist clones several kinds of extinct dinosaurs, proves how the idea struck a mixture of fear and excitement into people's hearts. But in fact we are a long way from being able to clone extinct animals. Scientists are still experimenting with 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 …

From time to time people suggest that extinct animals like dinosaurs, can possibly be brought back to life through cloning. Unfortunately, with what we know now, this is either impossible or unsuitable. There are many reasons.

◎ The initial requirement is that you need perfect DNA (which gives information for how cells

are to grow.

◎ All efforts of cloning an animal will be in vain if there is not enough diversity in the group to overcome illnesses. Diversity in a group means

having animals with their genes arranged in different ways. The advantage is that if there is a new illness some of these animals may die,

but others will survive and pass on the ability to 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 be left 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.

Based on what we know now, you cannot clone animals that have been extinct longer than 10,000 years. Actually, dinosaurs disappeared 65,000,000 years ago. So the chance of dinosaurs ever returning to the earth is merely a dream.

选修8 Unit 3

Inventors and inventions-Reading THE PROBLEM OF THE SHRIKES

When I called up my mother in the countryside on the telephone she was very upset. \

now and then, and they seem to have made their home here, not far from the walnut tree. Can you get rid of them please?\distinguish myself by inventing something merciful that would catch snakes but not harm them. I knew my parents would not like me to hurt these living creatures! The first thing I did was to see if there were any products that might help me, but there only seemed to be powders designed to kill snakes. A new approach was clearly needed. I set about researching the habits of snakes to find the easiest way to trap them. Luckily these reptiles are small and that made the solution easier. Prepared with some research findings, I decided on three possible approaches: firstly, removing their habitat; secondly, attracting them into a trap using male or female perfume or food; and thirdly cooling them so that they would become sleepy and could be easily caught. I decided to use the last one. I bought an ice-cream maker which was made of stainless steel. Between the outside and the inside walls of the bowl there is some jelly, which freezes when cooled. I put the bowl into the fridge and waited for 24 hours. At the same time I prepared some ice-cubes.

The next morning I got up early before the sun was hot. I placed the frozen bowl over the snakes' habitat and the ice-cubes on top of the bowl to keep it cool. Finally I

covered the whole thing with a large bucket. Then I waited. After two hours I removed the bucket and the bowl. The snakes were less active but they were still too fast for me. They abruptly disappeared into a convenient hole in the wall. So I had to adjust my plan.

For the second attempt I froze the bowl and the ice-cubes again but placed them over the snakes' habitat in the evening, as the temperature was starting to cool. Then as before, I covered the bowl with the bucket and left everything overnight. Early the next morning I returned to see the result. This time with great caution I bent down to examine the snakes and I found them very sleepy. But once picked up, they tried to bite me. As they were poisonous snakes, I clearly needed to improve my design again.

My third attempt repeated the second procedure. The next morning I carried in my hand a small net used for catching fish. This was in the expectation that the snakes would bite again. But monitored carefully, the snakes proved to be no trouble and all went according to plan. I collected the passive snakes and the next day we merrily released them all back into the wild.

Pressed by my friends and relations, I decided to seize the opportunity to get recognition for

my successful idea by sending my invention to the patent office. Only after you have had that

recognition can you say that you are truly an inventor. The criteria are so strict that it is difficult to get new ideas accepted unless they are truly novel. In addition, no invention will get a patent if it is:

◎a discovery

◎a scientific idea or mathematical model ◎literature or art