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  3. Stanford University’s Irving Weissman has said that he would like to inject human stem cells into the developing brains of fetal

Stanford University’s Irving Weissman has said that he would like to inject human stem cells into the developing brains of fetal

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问题     Stanford University’s Irving Weissman has said that he would like to inject human stem cells into the developing brains of fetal mice, with the goal of producing mouse brains composed chiefly of human brain cells. Such mice might be useful for testing drugs to cure or prevent various human brain diseases. Since the brains would have the architecture of mouse brains, it is unlikely that they would become biotech Stuart Littles and exhibit any characteristics that would cause us moral concerns.
    But what about injecting human brain stem cells into the developing brains of fetal chimpanzees? That’s clearly a bit closer to the line, but if human cells are simply integrated into the typical architecture of a chimpanzee’s brain, then again, it would probably create no new ethical problems.
    Beside the possibility of giving human characteristics to animals, injecting human stem cells into non-humans could create other moral concerns. For example, stem cells might transdifferentiate into gamete-producing cells, and integrate themselves into the ovaries and testes of mice, where they would produce completely human eggs and sperm. One could imagine such chimeric male and female mice mating and producing a completely human embryo. Of course, that embryo would be unable to develop in the uterus of a mouse, so the world would not have to deal with the birth of a child whose mom was a rodent. But again, what if this research were done with larger chimeric animals—say, cows—that could possibly carry a human baby to term?
    But chimeric mice could also be used to help people overcome infertility. Bone marrow stem cells from an infertile woman or man might be injected into a fetal mouse, where they could be transdifferentiated into gamete-producing cells. Gametes might be harvested from the mice and used in IVF procedures to engender a child. Assuming it’s medically safe, producing a child in this way would not be unethical.
    Finally, it has to be asked: would eating a liver composed chiefly of human liver cells grown in a sheep be cannibalism? I say yes; don’t do it. Save them for transplants.
    As humanity’s biotechnological prowess increases, we will confront again and again the question of what, if any, limits should be placed on research that mixes human and animal genes, cells and tissues. The main ethical concern about such research is not the creation of improved and useful animals, but the risk of producing what would be, in effect, diminished human beings.
Chimeric mice created could be used to______.
选项 A、engender a human child
B、help infertile couple procreate
C、provide gamete-producing ceils
D、prevent various human brain diseases
答案B
解析 根据第四段第一句“But chimeric mice could also be used to help people overcome infertility”，B应为答案。
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