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

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G2 is a phase that indicates the gap between when DNA synthesis occurs and when the next mitotic event occurs.

2期是在DNA合成期完成后,到分裂期开始前的间期

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