Mitosis160-page15

Mitosis160-page15 - growth phase. Once the diploid egg cell...

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Cell Reproduction: Mitosis - 15 Cloning animals has not been so easy. In contrast to plant cells, the DNA in animal tissues undergoes "permanent" changes during development so that taking one cell and treating it with hormones and nutrients does not result in the cell developing into a new organism. What passes for cloning in animals involves donor enucleated egg cells and a donor diploid nucleus. This was first accomplished in the 1950's with frogs, but there was little (no) success with mammals for decades. In 1996, Ian Wilmut cloned a sheep using the nucleus from an altered mammary cell of an adult sheet implanted into an egg cell from which the nucleus was removed. They induced the nuclei of the mammary cells to dedifferentiate by growing isolated mammary cells in a nutrient-poor medium that forced the cells into a G
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Unformatted text preview: growth phase. Once the diploid egg cell divided and started developing, the embryos were transplanted into a surrogate "mother" and one survived, the now famous Dolly. Since then many mammals have been "cloned" using this technique, and it has been announced that cloned human embryos had been formed. No human clones have been presented to the public, and such research is currently not allowed in the United States. The success rate of cloning is low. Both donor cell and donor nucleus undergoes trauma, and implantation has additional risks. Newer techniques cause less trauma to the donor nucleus and using a mixture of chemicals from rapidly dividing cells promotes more stable DNA in the donor nucleus. This technique is called chromatin transfer. "Cloning" Dolly...
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This note was uploaded on 12/29/2011 for the course BIO 151 taught by Professor Edwards during the Spring '10 term at SUNY Stony Brook.

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