可是它仅仅在晶胚中才具有活性。

But it is active only in embryos.

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对于干细胞研究的态度，他说在2004年，某位科学家告诉他这项研究不涉及到道德问题，因为用于研究的晶胚无论如何都将被销毁之后，他的看法有了改变。

On stem cells, he says he changed his mind in 2004, after a scientist told him there was no moral issue involved because the embryos used in the research would be destroyed anyway.

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胚胎干细胞研究的支持者们指出人的晶胚是在生育过程中形成的，大多数晶胚不是被破坏就是不明原因地被冻结了。

Proponents of embryonic stem-cell research point out that hordes of embryos are created during fertility treatment, and the vast majority of these are either frozen indefinitely or destroyed.

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