These were determined right after fertilization.

这些是在受精后立即决定的。

Just days after fertilization, the embryo implants in the lining of the uterus.

在受精后的几天内，胚胎就会被植入子宫内膜。

But until 6 or 7 weeks after fertilization, both 'XY' and 'XX' embryos have identical gonads.

但直到受精后6或7周，XY和XX胚胎都有相同的生殖腺。

And this mitochondrial DNA is specifically inherited from your mom because your dad's degraded immediately after fertilization.

这个线粒体DNA是特别从你妈妈那里遗传过来的，因为爸爸的在受精后就马上退化了。

Those embryos followed the development of natural mouse embryos up to eight and a half days after fertilization.

这些胚胎在受精后8天半的时间里和自然受精的老鼠胚胎的发育情况一致。

The writers of several studies described models that look similar to human embryos nine to 14 days after fertilization.

几项研究的作者描述了受精后9至14天看起来与人类胚胎相似的模型。

Their hearts start beating only 20 hours  after fertilization, well before the growing organism actually needs its heart functions.

他们的心脏在受精后仅 20 小时就开始跳动，远早于生长中的有机体真正需要其心脏功能。

Even after fertilization of the egg and all of the cell divisions it takes to make a person, that epigenetic mark remains – a reminder to keep those maternally-derived copies of the genes turned off.

尽管到胚胎形成前，会发生卵子受精、细胞分裂等生物学过程，表观遗传的改变会一直保留，使这些母源基因保持沉默。

Common convention is to transfer the embryo three days after fertilization, when the embryo has eight cells, or on day five, when the embryo is called a blastocyst, and has hundreds of cells.

通常的做法是在受精三天后移植胚胎，此时胚胎有八个细胞，或者在第五天移植胚胎， 此时胚胎被称为囊胚，有数百个细胞。