Question

6. The cell cycle can be arrested in mitosis when a single sister-chromatid pair is mono-oriented on the mitotic spindle. If at this point a glass microneedle is used to pull the mono-oriented chromosome toward the pole to which it is not attached, the cell proceeds to anaphase. This observation confirms that ...

Answer 1

Pulling a mono-oriented chromosome towards the opposite pole triggers anaphase by satisfying the M checkpoint, demonstrating the checkpoint's role in ensuring proper chromosome attachment before cell cycle progression.

Step-by-step explanation:

The observation that a cell proceeds to anaphase following mechanical manipulation of a mono-oriented chromosome suggests that the cell cycle progression relies on the correct attachment of chromosomes to spindle fibers. When all chromosomes are properly bi-oriented, with their kinetochores attached to spindle fibers from opposite poles, the M checkpoint is satisfied. The pulling of a mono-oriented chromosome towards the opposite pole simulates this correct orientation, fooling the checkpoint and allowing the cell to proceed to anaphase, where sister chromatids separate and are pulled toward the centrosomes.