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2019-2020年高中英語 Unit2第6課時（文化背景知識）教案 新人教版選修8 I. Reading prehension: Hello, Dolly! British scientists have done something that many people thought was impossible: they created the first clone of an adult mammal. The clone, named Dolly, is a seven-month-old sheep, grown from a cell of an adult female sheep. What is a clone? A clone is a copy, a genetic copy. Genes are the instructions for life. They tell a cell what to do and how to do it. Genes make each individual plant or animal different and unique. But a clone has the same genes as the original organism. Cloning is not new. Plants have been cloned for centuries. New plants are often grown from cuttings from another plant. Also, plants like pineapples, strawberries and carnations are sometimes cloned. One benefit of cloning is that we can make many copies of the best and healthiest plants. It has been much more difficult to clone animals. Frogs have been cloned, but they died as tadpoles, never living long enough to bee adult frogs. Mice, sheep and cattle have been cloned from embryos. But Dolly is the first healthy clone of an adult mammal. How did they do it? (1) An unfertilized egg was taken from a sheep. (2) The egg nucleus was removed. (3) A cell was taken from the udder of a pregnant sheep. It was “starved”, so that it stopped growing. (4) The two cells were bined into one and then implanted in a third sheep, where it grew normally. (5) The clone was born. It was genetically identical to the pregnant sheep in step (3). This sounds much easier than it actually was. To end up with one clone, the scientists started with 277 udder cells. And they needed in a way to make the egg cell accept a new nucleus. They did that by starving the cell in step (3). It may soon be possible to clone many types of animals. Will we also be able to clone human organs, or even whole human beings? We have only begun to think about the morality of cloning technology. Maybe the question to ask is not whether we can clone humans, but instead, should we clone humans? 1. Dolly is a sheep because she is grown from a cell of an adult female sheep _____. A. that has not her father B. that has not her mother C. that has no parents D. that has not any tail 2. Tell which of the following statements is TRUE. A. Only plants can be cloned. B. Only strawberries and carnations can sometimes be cloned. C. Animals and plants have quite a long history of cloning. D. Genes can tell a cell what to do and how to do it during cloning. 3. From the fourth paragraph we can know that _____. A. a tadpole is the early stage of a grown-up frog B. a tadpole is a frog without a tail C. a tadpole is a pool where frogs can live D. a tadpole is a clone of an adult mammal 4. What is the right order in the process of the clone of Dolly? a. Taking an unfertilized egg from an adult female sheep. b. Removing the egg’s nucleus. c. bining the two cells into one and then implanting it in a third sheep. d. Taking a cell from the udder of a pregnant sheep. A. a b c d B. c a b d C. a b d c D. d c b a 答案與分析 本文是科普時文閱讀。全文講述了克隆羊多莉的出生過程。 1. C 從文章中可以看出，多莉是從一只成年羊的細(xì)胞中克隆出來的，所以它根本沒有父母，而是那只羊的一個翻版。A項“它沒有父親”、B項"它沒有母親"說得太片面，D項“它沒有尾巴”不符合題意。 2. D 題意為“下面哪句話是對的”，D項“基因在克隆過程中可以告訴細(xì)胞做什么及如何去做”，文中第二 段正是說的這個意思。第三段指植物可以克隆，第四段指動物也可以克隆，所以選項A“只有植物可以克隆”不正確。從文中第三段可知菠蘿也是可以克隆的，所以B項“只有草莓和康乃馨有時可以克隆”不正確。第三段中指植物已有幾個世紀(jì)的克隆歷史，而沒有提到動物的克隆歷史，所以與C項“動、植物都有一個相當(dāng)長的克隆歷史”與題意不符。 3. A 文中第四段第二句中說：人們曾經(jīng)克隆過青蛙，但在蝌蚪階段就死了，并沒有活到成年青蛙階段，所以我們可以判斷，蝌蚪是青蛙的早期形態(tài)，故A項“蝌蚪是成年青蛙的早期形態(tài)”正確。B項“蝌蚪是沒有尾巴的青蛙”、C項“蝌蚪是青蛙生存的池塘”、D項“蝌蚪是成年哺乳動物的克隆體”與實際不符。 4. C 題意為“克隆多莉的正確順序是什么”，從文中第四段后半部分的內(nèi)容可知，正確順序應(yīng)是C項中所說的。 Ⅱ. About Cloning Quite a few people might take a negative attitude towards cloning. They argue that cloning will arouse a lot of moral and ethical problems and that some people would use the technique to develop crime (How will you feel to face a younger but identical twin of you yourself?). All that they worry about are true. But as every coin has two sides, cloning is no exception. Even the father of the world’s first clone Dolly is not for cloning. But he simply goes against cloning people. But what is clone anyway? Up to now Dolly is the only clone in the world. She was created not out of the natural way the union of a sperm and an egg that we are familiar with, but out of the genetic material from an udder cell of a six-year-old sheep. The embryologist Wilmut fused the udder cell with an egg from another sheep, after first removing all genetic material from the egg. The udder cell’s genes took up residence in the egg and directed it to grow and develop and an identical twin of the original sheep, Dolly was resulted. And that is how a clone is born. As cloning is no longer a science fiction, and with the birth of Dolly, the whole world begins to focus on these high technology and that generate a severe argument mentioned at the beginning of the article. Is it that frightening when speaking of cloning? The answer is yes. I’m not denying that clone has certain disadvantages. Actually clone is a double-edge sword, we have to admit. But we can make the best of its bright side. Will you admire the rose’s beauty as you used to when you discover its thorn? We all know that it is just because the rapid development of economy that has led to the polluted environment and therefore brings a lot of diseases and many an animal’s dying out. Can we just stop modernizing because of this? The answers are certainly no. Such is the case as cloning. We can gain a lot from it if used properly. We can clone organs patients need badly to help reduce their pain and even save their lives because they are the perfect match. We can also make an extinct creation back to live when necessary. The list goes on and on. There are never going be sufficient reasons that we should stop doing research on the field of cloning. Instead, the future of cloning is prosperous. Since the harm can not be avoided, at least we can try to put it to the least. But it turns out to be the government’s duty. In addition, the clone technique has not grown mature yet. What troubles us now is really how to make the program a successful one. Take a second thought, and you might be for cloning too. Ⅲ. Questions about Cloning 1. Why clone? Research advances over the past decade which have told us that, with a little work, we humans can clone just about anything we want, from frogs to monkeys and probably even ourselves! So, we can clone things, but why would we want to? Let’s look at some of the reasons people give to justify cloning. A. Cloning for medical purposes Of all the reasons, cloning for medical purposes has the most potential to benefit large numbers of people. How might cloning be used in medicine? a. Cloning animal models of disease Much of what researchers learn about human disease es from studying animal models such as mice. Often, animal models are genetically engineered to carry disease-causing mutations in their genes. Creating these transgenic animals is a time-intensive process that requires trial-and-error and several generations of breeding. Cloning technologies might reduce the time needed to make a transgenic animal model, and the result would be a population of genetically identical animals for study. b. Cloning stem cells for research Stem cells are the body’s building blocks, responsible for developing, maintaining and repairing the body throughout life. As a result, they might be used to repair damaged or diseased organs and tissues. Researchers are currently looking toward cloning as a way to create genetically defined human stem cells for research and medical purposes. c. “Pharming” for drug production Farm animals such as cows, sheep and goats are currently being genetically engineered to produce drugs or proteins that are useful in medicine. Just like creating animal models of disease, cloning might be a faster way to produce large herds of genetically engineered animals. B. Reviving endangered or extinct species Have you seen Jurassic Park? In this feature film, scientists use DNA preserved for tens of millions of years to clone dinosaurs. They find trouble, however, when they realize that the cloned creatures are smarter and fiercer than expected. Could we really clone dinosaurs? In theory? Yes. What would you need to do this? A well-preserved source of DNA from the extinct dinosaur and a closely related species, currently living, that could serve as a surrogate mother. In reality? Probably not. It’s not likely that dinosaur DNA could survive undamaged for such a long time. However, scientists have tried to clone species that became extinct more recently, using DNA from well-preserved tissue samples. C. Reproducing a deceased pet No joke! If you really wanted to, and if you had enough money, you could clone your beloved family cat. At least one biotechnology pany in the United States offers cat cloning services for the privileged and bereaved, and they are now working to clone dogs. But don’t assume that your cloned kitty will be exactly the same as the one you know and love. The main reason to clone plants or animals is to mass produce organisms with desired qualities, such as a prize-winning orchid or a genetically engineered animal — for instance, sheep have been engineered to produce human insulin. If you had to rely on sexual reproduction (breeding) alone to mass produce these animals, and then you would run the risk of breeding out the desired traits because sexual reproduction reshuffles the genetic deck of cards. Other reasons for cloning might include replacing lost or deceased family pets and repopulating endangered or even extinct species. Whatever the reasons, the new cloning technologies have sparked many ethical debates among scientists, politicians and the general public. Several governments have considered or enacted legislation to slow down, limit or ban cloning experiments outright. It is clear that cloning will be a part of our lives in the future, but the course of this technology has yet to be determined. 2. How are clones created? The most mon process takes DNA from one cell and puts in a hollowed-out egg. Chemicals and electricity are then used to encourage the new DNA to fuse with the egg and develop into an embryo. This technique is called nuclear transfer. 3. Are clones normal, healthy animals? Dolly is, but scientists do not yet know whether this is the exception or the rule. Some early evidence suggests that clones may have health problems and that they may age prematurely. 4. Could a human clone be born soon? In theory, yes. The techniques used to create Dolly could be applied to humans. But the technology of reproductive cloning is still in its very early stages and there is much that scientists do not understand. It took more than 200 attempts to make Dolly. The other embryos failed to implant in the surrogate mother or were miscarried. Even if a clone makes it to birth, at present it has a very low chance of surviving into adult life. 5. Has anyone said they will make live human clones? A number of people have, including Chicago physicist Dr Richard Seed. However, few experts believe that these people have the skills to succeed. 6. Are there any benefits from cloning? Yes. The techniques used have already demonstrated benefits. Polly, another sheep clone at the Roslin Institute in Edinburgh has had a human gene inserted so that it produces a blood clotting agent needed by haemophiliacs in its milk. Cloning of human cells in a laboratory could offer perfectly-matched tissue for surgical or genetic repair of humans. 7. Where does the law stand on live human clones? In the UK, human cloning is already banned(禁止) by law. President Bill Clinton has proposed banning research into producing human clones in the US for five years. Some measures have also been made to establish international agreements banning live human clones. 8. What animals have been cloned? Scientists have been cloning animals for many years. In 1952, the first animal, a tadpole, was cloned. Before the creation of Dolly, the first mammal cloned from the cell of an adult animal, clones were created from embryonic cells. Since Dolly, researchers have cloned a number of large and small animals including sheep, goats, cows, mice, pigs, cats, rabbits, and a gaur. All these clones were created using nuclear transfer technology. Hundreds of cloned animals exist today, but the number of different species is limited. Attempts at cloning certain species such as monkeys, chickens, horses, and dogs, have been unsuccessful. Some species may be more resistant to somatic cell nuclear transfer than others. The process of stripping the nucleus from an egg cell and replacing it with the nucleus of a donor cell is a traumatic one, and improvements in cloning technologies may be needed before many species can be cloned successfully. 9. Can organs be cloned for use in transplants? Scientists hope that one day therapeutic cloning can be used to generate tissues and organs for trans-plants. To do this, DNA would be extracted from the person in need of a transplant and inserted into an enucleated egg. After the egg containing the patient’s DNA starts to divide, embryonic stem cells that can be transformed into any type of tissue would be harvested. The stem cells would be used to generate an organ or tissue that is a genetic match to the recipient. In theory, the cloned organ could then be transplanted into the patient without the risk of tissue rejection. If organs could be generated from cloned human embryos, the need for organ donation could be significantly reduced. Many challenges must be overe before “cloned organ” transplants bee reality. More effective technologies for creating human embryos, harvesting stem cells, and producing organs from stem cells would have to be developed. The scientists then harvested fetal tissue from the clones and transplanted it into the donor cow. In the three months of observation following the transplant, no sign of immune rejection was observed in the transplant recipient. More research is needed to study the transplantation of organs from “knock-out” pigs o other animals. 10. What are the risks of cloning? Reproductive cloning is expensive and highly inefficient. More than 90% of cloning attempts fail to produce viable offspring. More than 100 nuclear transfer procedures could be required to produce one viable clone. In addition to low success rates, cloned animals tend to have more promised immune function and higher rates of infection, tumor growth, and other disorders. Japanese studies have shown that cloned mice live in poor health and die early. About a third of the cloned calves born alive have died young, and many of them were abnormally large. Many cloned animals have not lived long enough to generate good data about how clones age. Appearing healthy at a young age unfortunately is not a good indicator of long term survival. Clones have been known to die mysteriously. For example, Australia’s first cloned sheep appeared healthy and energetic on the day she died, and the results from her autopsy failed to determine a cause of death. Problems also may result from programming errors in the genetic material from a donor cell. 11. Should humans be cloned? This is a serious topic. I read a report (Reuters, United Nations, October 8, xx) about the human cloning. A group of scientists, doctors and legal experts asked the United Nations on Wednesday to seek an advisory opinion from the World Court declaring human cloning to be a “crime against humanity.” Physicians from the American Medical Association and scientists with the American Association for the Advancement of Science have issued formal public statements advising against human reproductive cloning. Currently, the U.S. Congress is considering the passage of legislation that could ban human cloning. In China, the Chinese Government has officially banned research on human cloning for procreation purposes, but allowed remedial cloning. 12. What benefits can humans gain from cloning? Research advances over the past decade have told us that, with a little work, we humans can clone just about anything we want, from frogs to monkeys and probably even ourselves! So, we can clone things, but why would we want to? Let’s look at some of the reasons people give to justify cloning. 1. Cloning for medical purposes 2. Reviving endangered or extinct species 3. Reproducing a deceased pet. Of all the reasons, cloning for medical purposes has the most potential to benefit large numbers of people. 13. How might cloning be used in medicine? Much of what researchers learn about human disease es from studying animal models such as mice. Cloning technologies might reduce the time needed to make a transgenic animal model, and the result would be a population of genetically identical animals for study. Researchers are currently looking toward cloning as a way to create genetically defined human stem cells for research and medical purposes. Farm animals such as cows, sheep and goats are currently being genetically engineered to produce drugs or proteins that are useful in medicine. Just like creating animal models of disease, cloning might be a faster way to produce large herds of genetically engineered animals. 14. Could humans be cloned now? Unquestionably, yes. Since the first cloned sheep, Dolly, surprised the world back in 1997, the cloning of animals has bee almost routine. panies have been able to churn out cloned cows, goats, and other critters, some of them genetically engineered to make valuable pharmaceutical products. “With cows, it has been very easy to do,” says Princeton biology professor Lee Silver. Human biology is even better understood than that of cows, so the cloning of people is pretty much inevitable. Indeed, the actual procedure is only a small step beyond what’s already routinely done in test tube baby clinics.