什么是克隆技术？ |
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What is Cloning?
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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