Isolating these cells, which are capable of maturing into any other type of cell, marked a landmark in biology — but a controversial one, since the process destroys a human embryo.

他于1998年首次分离出人类胚胎干细胞，该细胞具有分化为任何其他类型成熟细胞的能力。

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A mature embryo sac is composed of egg apparatuses (two synergids and one egg cell), central cells and three antipodal cells.

成熟胚囊包含卵器(由两个助细胞、一个卵细胞组成)，中央细胞及三个反足细胞。

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There are risks involved with preimplantation testing, which generally involves removal of one or more cells from an eight-cell embryo called a blastocyst.

着床前检查一般要从一个称为胚泡的8细胞胚胎中取出1个或更多细胞，该过程也存在一定风险。

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Once you've got them, you don't need to destroy any more embryos, but each time you get a new one of these embryonic stem-cell lines, you need to destroy an embryo.

NPR: Ethical Guidelines for Stem Cell Research Proposed