The spindle checkpoint can delay anaphase while kinetochore attachment is incomplete. This couples progression to the state of the spindle apparatus, rather than requiring every biological cell to separate its sister chromatids after a fixed waiting time. Alignment in a picture alone is not a demonstration that this control is satisfied.[ref]
Control of the Cell Cycle. Biology 2e, §10.3, Regulation at Internal Checkpoints, Figure 10.11 and The M Checkpoint
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