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One of the greatest introduction to the scientific world in recent times must surely be the introduction of Dolly, a sheep in Britain. Dolly is no ordinary sheep. It is an exact replicate, genetically of another adult sheep. The successful cloning of Dolly has captured the imagination of a worldwide community. Its implications are simply mind-boggling.

Prior to Dolly's birth, scientists once thought that the biological development of cells was irreversible. As an organism grows, its cells divide. Then, the cells become more specialized by switching on certain genes inside their nuclei and shutting down others. People assumed that the genes were shut down for good, but Dolly's arrival appears to show that the process was reversible. To make Dolly, Ian Wilmut and his colleagues had to wind back the development of an adult cell. The cell was biochemically reprogrammed to begin life all over again.

Pioneering experiments had begun as early as in 1970, when a team led by John Gurdon at the University of Cambridge transplanted nuclei from the skin cells of adult frogs into frog eggs lacking their own nuclei. While some grew into tadpoles, none reached adulthood. Wilmut says the key to his success lies in the unique way his team manipulates the cells.

Now that an adult sheep has been cloned, there appears no reason why we could not do the same with humans. Scientists can select a cell from a human donor, fuse it with an unfertilized egg and implant it into a surrogate mother's womb. However, we are not there yet. Working out the biochemistry and limits of this `reprogramming of cells' will keep the researchers busy for years. Nobody knows for sure whether clones could be made with any human adult cell. "Brain and muscle cells are probably so specialized that you can't reset their clocks," says Wilmut.

The idea itself is truly amazing and it is not impossible. However, some people feel a kind of horror about producing clones. In Britain, there is already a law against human cloning. In the States, the government is reviewing the implications of the breakthrough. President Clinton has said, "I believe we must respect this profound gift (human life) and resist the temptation to replicate ourselves." If human cloning is possible, these are the ethical questions that need to be considered. `Who would assume responsibility for her welfare? Who would be her parents and how would she cope psychologically and socially?'

On the other hand, there are also interesting possibilities. "In many ways cloning could offer enormous benefits," says one scientist. "You could clone from an adult or a child who is sick to produce cells that can be used to repair the individual's damaged tissues." Potentially, scientists could even create brain-dead copies of humans as sources of perfectly-matched organs transplants. Even then there are objections to this. If brain-dead clones were nurtured and used as organ banks, "This would radically change the nature of what it is like to be human."

The breakthrough that Dolly has achieved has been described as 'one giant leap into the unknown'. "Most of the things this technique will be used for have not yet been imagined," says Wilmut. Nevertheless, with all the heated debate that it has generated, it seems apparent that mankind is not ready to face a real living human clone yet.

  1. What is cloning, according to the first paragraph ?
  2. Explain what does mind-boggling means ?
  3. What happens when an organism grows ?
  4. How was the process in Dolly's case 'reversible' ?
  5. What happened to the eggs with the transplanted nuclei in the pioneering experiments ?
  6. Before we can start cloning humans, what do the scientists need to work out first ?
  7. What is happening in the States regarding the idea of human cloning ?
  8. Give two ethical questions that need to be considered if a human is cloned ?
  9. How can a brain-dead clone help us ?
  10. Say in what way man shows that he is not ready for human cloning yet and then write out a phrase from the text to support your answer.
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  1. Cloning is to reproduce an exact copy, genetically of another living creature.
  2. It means having a profound or staggering effect on the mind.
  3. The cells divide and become more specialized by switching on certain genes inside their nuclei and shutting down others.
  4. The genes that were shut down in the nuclei could be activated again.
  5. Some of the eggs grew into tadpoles but they all died before reaching adulthood.
  6. Scientists need to work out the biochemistry and limits of the 'reprogramming of cells'.
  7. In the States, the government is studying the implications of human cloning.
  8. Any 2 :

who should be responsible for the cloned person's welfare

who the parents would be

how the cloned person would cope psychologically and socially.

  9. A brain-dead clone can provide us with perfectly-matched organs for transplant when we need them.
  10. The cloning of Dolly, a sheep has already caused a huge discussion. The words 'heated debate' suggest this.

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Comprehension 1


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