Established upon the embryo stem cell technique and homologous recombination, gene targeting has been widely used in the genome specific manipulation.

基因打靶技术是建立在胚胎干细胞和同源重组技术之上，可对基因组进行定点修饰的实验方法。

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However, nuclear reprogramming, which stands in the way of reconstructed embryo stem cell research, is still a bottleneck in the procedure of nuclear transfer.

但是核重编程仍是核移植技术的瓶颈，制约了重构胚胎干细胞的研究。

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And unfortunately, in order to get those stem cells, that requires killing the embryo.

而不幸的是，要想得到这些干细胞，就需要杀死胚胎。

干细胞和伦理 - SpeakingMax英语口语达人

"It doesn't have to be, you know, embryo stem-cell research or fetal or cloning, " Lott said.

CNN: Lott says he's opposed to federal funding of stem-cell research

In mice, Daley and colleagues have shown that stem cells derived from the nuclear transfer of cells to make embryos -- the technique described in Mitalipov's paper -- were indeed closer to natural embryo stem cells than induced pluripotent stem cells.

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Earlier this week a team in the U.S. led by Shoukhrat Mitalipov of the Oregon National Primate Research Center, announced they had created the first cloned monkey embryo and extracted stem cells from it.

CNN: You, again: Are we getting closer to cloning humans?