Mitosis and Checkpoints: Ensuring Proper Cell Division

What is the mechanism that delays the onset of anaphase if a chromosome fails to become aligned properly at the metaphase in mitosis?

A. Spindle checkpoint

B. Cyclin-dependent kinase checkpoint

C. G2 checkpoint

D. START checkpoint

E. ATR/ATM checkpoint

Final answer: A. Spindle checkpoint

In mitosis, the spindle checkpoint delays the onset of anaphase if a chromosome is not properly aligned during metaphase.

Understanding the Spindle Checkpoint in Mitosis

During cell division, the spindle checkpoint plays a crucial role in ensuring the accurate distribution of chromosomes to the daughter cells. This checkpoint, also known as the M checkpoint, monitors the attachment of sister chromatids to the spindle microtubules during metaphase.

The spindle checkpoint prevents premature progression to anaphase until all sister chromatids are correctly attached to the spindle fibers. This ensures that each pair of sister chromatids is aligned and ready for the process of chromatid separation during anaphase.

If a chromosome fails to become properly aligned at the metaphase, the spindle checkpoint will halt the cell cycle progression by inhibiting the activity of a protein complex known as separase. This delay allows the cell to correct any errors in chromosome alignment before proceeding to anaphase.

Overall, the spindle checkpoint serves as a safeguard mechanism to maintain the genomic stability of the cell by ensuring that chromosome segregation occurs accurately during cell division.