How is the cell cycle regulated in eukaryotic cells?

• A. Through the random activation of cyclins without any specific order
• B. By the constant and unregulated division of cells
• C. Through checkpoints that ensure each phase is completed before the next begins
• D. By the inhibition of all cyclin-dependent kinases

Answer: (C)

Verified step by step guidance

1. Understand that the cell cycle in eukaryotic cells is a series of phases that a cell goes through to divide and produce new cells. These phases include G1, S, G2, and M phases.
2. Recognize that the regulation of the cell cycle is crucial to ensure that cells divide correctly and at the right time. This regulation is achieved through a series of checkpoints.
3. Learn that checkpoints are control mechanisms in the cell cycle that verify whether the processes at each phase have been accurately completed before the cell proceeds to the next phase.
4. Identify the key checkpoints: the G1 checkpoint (checks for cell size, nutrients, growth factors, and DNA damage), the G2 checkpoint (ensures all DNA is replicated and checks for DNA damage), and the M checkpoint (ensures all chromosomes are attached to the spindle apparatus).
5. Understand that cyclins and cyclin-dependent kinases (CDKs) are proteins that play a significant role in the regulation of the cell cycle. Cyclins bind to CDKs, activating them to phosphorylate target proteins that advance the cell cycle past a checkpoint.