Early embryogenesis is marked by a frail Spindle Assembly Checkpoint (SAC). The time of SAC acquisition varies depending on the species, cell size or a yet to be uncovered developmental timer. This means that for a specific number of divisions, biorientation of sister chromatids occurs unsupervised. When error‐prone segregation is an issue, an aneuploidy‐selective apoptosis system can come into play to eliminate chromosomally unbalanced cells resulting in healthy newborns. However, aneuploidy content can be too great to overcome, endangering viability.

中文翻译：

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早期细胞分裂期间的 SAC：牺牲及时分裂的保真度，在不同生物体中受到不同的调控

早期胚胎发生的标志是脆弱的纺锤体组装检查点 (SAC)。SAC 采集的时间因物种、细胞大小或尚未发现的发育计时器而异。这意味着对于特定数量的分裂，姐妹染色单体的生物定向是在无人监督的情况下发生的。当容易出错的分离成为问题时，非整倍体选择性细胞凋亡系统可以发挥作用，以消除染色体不平衡的细胞，从而产生健康的新生儿。然而，非整倍体含量可能太大而无法克服，从而危及生存能力。