When I talked about mitosis, I talked about cells making perfect copies of each other, so each parent cell becoming two daughter cells that are the same.

我讲有丝分裂的时候,谈到过细胞能够完美的复制自己,母细胞分裂成为,两个完全一样的子细胞

耶鲁公开课 - 生物医学工程探索课程节选

That's one of the properties of mitosis, that the DNA gets completely duplicated during the S phase, during DNA synthesis phase.

有丝分裂的一个特征,就是DNA在S期内完全复制,S期就是DNA合成期

耶鲁公开课 - 生物医学工程探索课程节选