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unit2 ：Cloning has always been with us and is here to stay.It is a way of making an exact copy of another animal or plant.It happens in plants when gardeners take cuttings from growing plants to make new ones.It also happens in animals when teins idrntical in sex and appearance are produced from the same original egg.The fact is that these are both examples of natural clones.
Cloning has two major uses.Firstly, gardeners use it all the time to produce commercial quantities of plants. Secondly, it is valuable for research on new plant species and for medical research on animals. Cloning plants is straightforward while cloning animals is very complicated.
It is a difficult task to undertake. Many attempts to clone mammals failed. But at last the determination and patience of the scientists paid off in 1996 with a breakthrough— the cloning of Dolly the sheep. The procedure works like this:
1 Female sheep A provides an egg cell.
2 The nucleus is removed from the egg cell.
3 The egg cell is ready for a new nucleus.
4 Female sheep B provides a somatic cell for the clone. The nucleus of this cell contains all the genes needed to produce a new sheep.
5 The nucleus is taken out of the somatic cell.
6 The nucleus from sheep B and the egg cell from sheep A are joined using electricity.
7 The cell divides and grows into an embryo.
8 The embryo is put into female sheep C,who becomes the carrier of the clone.
9 The lamb is the clone of the donated cell from sheep B which provided the nucleus.
Cloning has two major uses.Firstly, gardeners use it all the time to produce commercial quantities of plants. Secondly, it is valuable for research on new plant species and for medical research on animals. Cloning plants is straightforward while cloning animals is very complicated.
It is a difficult task to undertake. Many attempts to clone mammals failed. But at last the determination and patience of the scientists paid off in 1996 with a breakthrough— the cloning of Dolly the sheep. The procedure works like this:
1 Female sheep A provides an egg cell.
2 The nucleus is removed from the egg cell.
3 The egg cell is ready for a new nucleus.
4 Female sheep B provides a somatic cell for the clone. The nucleus of this cell contains all the genes needed to produce a new sheep.
5 The nucleus is taken out of the somatic cell.
6 The nucleus from sheep B and the egg cell from sheep A are joined using electricity.
7 The cell divides and grows into an embryo.
8 The embryo is put into female sheep C,who becomes the carrier of the clone.
9 The lamb is the clone of the donated cell from sheep B which provided the nucleus.
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这也不够啊。
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Unit3我只找到了翻译：
http://wenku.baidu.com/view/78b0c0c158f5f61fb7366665.html
抱歉啊
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