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  3. Wiping away doubts that Dolly the sheep clone was a fluke, University of Hawaii researchers announced they’ve been cloning mice

Wiping away doubts that Dolly the sheep clone was a fluke, University of Hawaii researchers announced they’ve been cloning mice

admin2013-01-12  32
问题     Wiping away doubts that Dolly the sheep clone was a fluke, University of Hawaii researchers announced they’ve been cloning mice for months, creating a flock of more than 50 duplicate rodents along the way. 71. The success of the Hawaii group transforms adult cloning from a scientific novelty to a well-defined procedure likely to be .reproduced in labs around the world. The mass production of carbon copy mice, in turn, now allows researchers to test variations of the cloning techniques to see what works best. Cloning the genetically engineered mice used in medical studies should also be cheaper than current breeding methods.
    The Hawaii researchers use essentially the same recipe used to make Dolly: Take an egg. Scoop out the nucleus, which contains the DNA genetic information, and discard. Take a cell of the animal you wish to clone and insert its DNA into the egg. Add chemicals to tell the egg to start developing into an embryo. Incubate the embryo in a test tube for a few days, and then implant it into a foster mother. Wait for the foster mother to give birth to the clone. 72. Where they modified the recipe was the method for moving the DNA from the animal-to-be-cloned into the egg. Most researchers had thought that mice would be particularly difficult to clone, because the DNA in mice embryos switches on very early, possibly as soon as the egg splits into the two-cell stage.
    Because adult cells have specific, specialized functions, most of the unused DNA has been turned off. Scientists had thought that the implanted DNA would not have enough time to "repro- gram" itself back to the embryonic, unspecialized state. Thus, most cloning research has focused on animals where the DNA switches on later, allowing more time for the reprogramming. 73. In cows, for example, the DNA switch-on occurs when the embryo reaches the eight-cell stage. No one is sure how the ttawaii group got the mouse DNA to reprogram itself more quickly, but some have the suspicion that getting rid of the outer part of the adult cell speeds the process.
    In addition to various genetic tests, the researchers used a simple color scheme to verify that the DNA of the babies was not contaminated by either the egg donor or the foster mother. The eggs came from black mice, while the foster mothers were all white mice. The baby mice all came out coffee-colored, the color of their identical DNA mother. The researchers have licensed their technology to venture capital company ProBio America Inc. , based in Honolulu. "This technique we are expanding into the large commercial animals, such as cows and sheep, where much of our business is intended to be," says ProBio’s Cameron Reynolds.
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答案例如，牛的胚胎在发育成8个细胞的阶段时DNA才山现转换。没有人知道夏威夷的研究人员是如何使老鼠的DNA更快地重编自己的程序的，但有些人怀疑是剔除成年细胞的外层加快了进程。
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