Final answer:
In Saccharomyces pombe, the cell cycle is governed by three main checkpoints: the G₁ checkpoint that checks conditions and DNA integrity, the G₂ checkpoint that ensures chromosome duplication and energy reserves, and the M checkpoint that verifies spindle attachment to kinetochores.
Step-by-step explanation:
The cell cycle in the yeast Saccharomyces pombe is controlled at three main checkpoints. These checkpoints ensure the proper conditions are met before the cell proceeds to the next phase of the cycle, which is crucial for maintaining genetic stability and preventing errors in cell division.
The G₁ checkpoint evaluates if the conditions are favorable for cell division, including checking for any DNA damage. If the cell doesn't meet the requirements, it might halt the cycle to repair itself or enter a quiescent state (G0 phase).
The G₂ checkpoint ensures that all chromosomes have been properly replicated and that the cell has enough energy reserves for mitosis. Lastly, the M checkpoint confirms that each chromosome's kinetochore is correctly attached to a spindle fiber before allowing the cell to progress to anaphase during mitosis. These checkpoints are pivotal for the cell to avoid an 'identity crisis' as described by Elledge SJ in Science (1996).