A 36‑year‑old woman is undergoing evaluation for a rapidly g…
A 36‑year‑old woman is undergoing evaluation for a rapidly growing ovarian tumor. Pathology shows that many tumor cells are stuck in metaphase with paired sister chromatids still attached, despite having normal spindle formation. Additional testing reveals a loss‑of‑function mutation affecting a ubiquitin‑ligase complex responsible for triggering chromatid separation and promoting mitotic exit. Which defect best explains the cell‑cycle abnormality seen in her tumor?