关于克隆的英语文章简单一点的.

关于克隆的英语文章简单一点的.
关于克隆的英语文章
简单一点的.

关于克隆的英语文章简单一点的.
我留学时写的:
Have you ever wished you could have a clone of yourself to do homework while you hit the skate park or went out with your friends? Imagine if you could really do that. Where would you start? One word "Cloning" are showed. What is cloning? Cloning is the creation of an organism that is an exact genetic copy of another. This means that every single bit of DNA is the same between the two! You might not believe it, but there are human clones among us right now. They weren't made in a lab, though: they're identical twins, created naturally. Below, we'll see how natural identical twins relate to modern cloning technologies.

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:
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?
• Cloning animal models of disease
Much of what researchers learn about human disease comes 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.
• 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.
• "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.
2. 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.
• 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. For an example, see "Can we really clone endangered or extinct animals?" on the right side of this page.
3. 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 company 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.
4. Cloning Humans?
To clone or not to clone: that is the question. The prospect of cloning humans is highly controversial and raises a number of ethical, legal and social challenges that need to be considered. Why would anyone want to clone humans? Some reasons include:
• To help infertile couples have children
• To replace a deceased child

Although cloning has some advantages, but on the other hand, when we hear of cloning successes, we learn about only the few attempts that worked. What we don't see are the many, many cloning experiments that failed! And even in the successful clones, problems tend to arise later, during the animal's development to adulthood. Cloning animals shows us what might happen if we try to clone humans. What have these animals taught us about the risks of cloning?
1. High failure rate
Cloning animals through somatic cell nuclear transfer is simply inefficient. The success rate ranges from 0.1 percent to 3 percent, which means that for every 1000 tries, only one to 30 clones are made. Or you can look at it as 970 to 999 failures in 1000 tries. That's a lot of effort with only a speck of a return!
Why is this? Here are some reasons:
• The enucleated egg and the transferred nucleus may not be compatible
• An egg with a newly transferred nucleus may not begin to divide or develop properly
• Implantation of the embryo into the surrogate mother might fail
• The pregnancy itself might fail
2. Problems during later development
Cloned animals that do survive tend to be much bigger at birth than their natural counterparts. Scientists call this "Large Offspring Syndrome" (LOS). Clones with LOS have abnormally large organs. This can lead to breathing, blood flow and other problems.
Because LOS doesn't always occur, scientists cannot reliably predict whether it will happen in any given clone. Also, some clones without LOS have developed kidney or brain malformations and impaired immune systems, which can cause problems later in life.
3. Abnormal gene expression patterns
Are the surviving clones really clones? The clones look like the originals, and their DNA sequences are identical. But will the clone express the right genes at the right time?
In a naturally-created embryo, the DNA is programmed to express a certain set of genes. Later on, as the embryonic cells begin to differentiate, the program changes. For every type of differentiated cell - skin, blood, bone or nerve, for example - this program is different.
In cloning, the transferred nucleus doesn't have the same program as a natural embryo. It is up to the scientist to reprogram the nucleus, like teaching an old dog new tricks. Complete reprogramming is needed for normal or near-normal development. Incomplete programming will cause the embryo to develop abnormally or fail.
4. Telomeric differences
As cells divide, their chromosomes get shorter. This is because the DNA sequences at both ends of a chromosome, called telomeres, shrink in length every time the DNA is copied. The older the animal is, the shorter its telomeres will be, because the cells have divided many, many times. This is a natural part of aging.
So, what happens to the clone if its transferred nucleus is already pretty old? Will the shortened telomeres affect its development or lifespan?
When scientists looked at the telomere lengths of cloned animals, they found no clear answers. Chromosomes from cloned cattle or mice had longer telomeres than normal. These cells showed other signs of youth and seemed to have an extended lifespan compared with cells from a naturally conceived cow. On the other hand, Dolly the sheep's chromosomes had shorter telomere lengths than normal. This means that Dolly's cells were aging faster than the cells from a normal sheep.
To date, scientists aren't sure why cloned animals show differences in telomere length.
We have to associate with clone human when we hear cloning. It also has risks and disadvantages:
1. Health risks from mutation of genes - an abnormal baby would be a nightmare come true. The technique is extremely risky right now. A particular worry is the possibility that the genetic material used from the adult will continue to age so that the genes in a newborn baby clone could be - say - 30 years old or more on the day of birth. Many attempts at animal cloning produced disfigured monsters with severe abnormalities. So that would mean creating cloned embryos, implanting them and destroying (presumably) those that look imperfect as they grow in the womb. However some abnormalities may not appear till after birth. A cloned cow recently died several weeks after birth with a huge abnormality of blood cell production. .
Even if a few cloned babies are born apparently normal we will have to wait up to 20 years to be sure they are not going to have problems later -for example growing old too fast. Every time a clone is made it is like throwing the dice and even a string of "healthy" clones being born would not change the likelihood that many clones born in future may have severe medical problems. And of course, that's just the ones born. What about all the disfigured and highly abnormal clones that either spontaneously aborted or were destroyed / terminated by scientists worried about the horrors they might be creating.
2. Emotional risks - a child grows up knowing her mother is her sister, her grandmother is her mother. Her father is her brother-in-law. Every time her mother looks at her she is seeing herself growing up. Unbearable emotional pressures on a teenager trying to establish his or her identity. What happens to a marriage when the "father" sees his wife's clone grow up into the exact replica (by appearance) of the beautiful 18 year old he fell in love with 35 years ago? A sexual relationship would of course be with his wife's twin, no incest involved technically.
Or maybe the child knows it is the twin of a dead brother or sister. What kind of pressures will he or she feel, knowing they were made as a direct replacement for another? It is a human experiment doomed to failure because the child will NOT be identical in every way, despite the hopes of the parents. One huge reason will be that the child will be brought up in a highly abnormal household: one where grief has been diverted into making a clone instead of adjusting to loss. The family environment will be totally different than that the other twin experienced. That itself will place great pressures on the emotional development of the child. You will not find a child psychiatrist in the world who could possibly say that there will not be very significant emotional risk to the cloned child as a result of these pressures.
3. Risk of abuse of the technology - what would Hitler have done with cloning technology if available in the 1940s? There are powerful leaders in every generation who will seek to abuse this technology for their own purposes. Going ahead with cloning technology makes this far more likely. You cannot have so-called therapeutic cloning without reproductive cloning because the technique to make cloned babies is the same as to make a cloned embryo to try to make replacement tissues. And at the speed at which biotech is accelerating there will soon be other ways to get such cells - adult stem cell technology. It is rather crude to create a complete embryonic identical twin embryo just to get hold of stem cells to make - say - nervous tissue. Much better to take cells from the adult and trigger them directly to regress to a more primitive form without the ethical issues raised by inserting a full adult set of genes into an unfertilized egg.
US President Bush said: "I believe all human cloning is wrong, and both forms of cloning ought to be banned, for the following reasons. First, anything other than a total ban on human cloning would be unethical. Research cloning would contradict the most fundamental principle of medical ethics, that no human life should be exploited or extinguished for the benefit of another." Also in my opinion, disadvantages are more than advantages. Cloning should be banned.
Reference:
L, Sloman. 2000, “ Medicinal World”, Science and Technology, Canberra.
Yoshukoo. 2002, “Human Health”, Culture Publishion, Tokyo.
Li Guojing. 2000, “Medicinal Development”, Medicinal University of China, Beijing
Online: www.learningworld.org /medicinal/cloning.
Online: www.muc.edu.cn/worldnews/cloning.

What is Cloning? 什么是克隆技术？

Cloning(克隆技术) is the most attractive story of the new biotechnologies(生物技术) and the one which causes the most heated discussion over its worth. Here are answers to ...

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What is Cloning? 什么是克隆技术？

Cloning(克隆技术) is the most attractive story of the new biotechnologies(生物技术) and the one which causes the most heated discussion over its worth. Here are answers to the most common questions about cloning.
1. What is cloning?
Cloning is the creation of cells or whole animals using DNA(脱氧核糖核酸) from a single "parent", bypassing(绕道而行) the normal reproductive process. The clone has the same DNA to the parent.
2. Is cloning unnatural?
No. Clones are always produced by natural means in the shape of identical twins(同卵孪生).
3. How are clones created?
The most common process takes DNA from one cell and puts in a hollowed-out(挖空的；掏空的) egg. Chemicals and electricity are then used to encourage the new DNA to fuse with(与…合并) the egg and develop into an embryo(胎儿). This technique is called nuclear transfer(核迁移).
4.Why was Dolly(世界上的第一只克隆羊) important?
The sheep was the first mammal(哺乳动物) to be cloned using DNA taken from an adult cell. Previously(以前), animals had only been cloned using embryo cells which already have the potential(潜力) to become a complete embryo in its own right(继承父母的). The big breakthrough with Dolly was to make a clone from an ordinary, adult cell - in this case from a female goat's udder(乳房).
5. Are clones normal, healthy animals?
Dolly is, but scientist do not yet know whether this is the exception(例外) or the rule. Some early evidence suggest that clones may have health problems and that they may age prematurely(早衰的，未老先衰).
6.Could a human clone be born soon?
In theory, yes. The techniques used to create Dolly could be applied to(运用；适用) 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(努力；试验) to make Dolly. The other embryos failed to implant(播种) in the surrogate(代理；代替) 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.
7.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.
8. Are there any benefits from cloning?
Yes. The techniques used have already demonstrated(展示) benefits. Polly, another sheep clone at the Roslin Institute in Edinburgh has had a human gene(基因) inserted so that it produces a blood clotting((血的)凝结) agent needed by haemophiliacs(血友症) in its milk. Cloning of human cells in a laboratory could offer perfectly-matched tissue(（动物的）组织) for surgical or genetic repair of humans.
9.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.

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