Final answer:
Cell-cycle checkpoint proteins are also known as positive regulators and include key proteins such as cyclins and cyclin-dependent kinases (Cdks). These proteins are crucial for monitoring and controlling the cell's progression through various checkpoints like G1, G2/M, and metaphase to ensure cellular readiness for advancement.
Step-by-step explanation:
Another Name for Cell-Cycle Checkpoint Proteins
The proteins responsible for controlling the progression of the cell through the various cell-cycle checkpoints are frequently referred to as positive regulators.
These include cyclins and cyclin-dependent kinases (Cdks). Cyclins exhibit a predictable pattern of fluctuation in their concentration levels throughout the cell cycle.
The role of Cdks remains constant, though they are activated by binding to cyclins.
This cyclin/Cdk complex formation triggers the progression through different checkpoints by phosphorylating specific target proteins essential for the next phase of the cell cycle.
The G1, G2/M, and metaphase checkpoints are crucial for ensuring that all necessary conditions are met before the cell moves onto the next stage.
Not only do these checkpoints allow the cell cycle to advance when all is well, they also play a critical role in preventing cell cycle progression if there is, for example, DNA damage or other cellular stress, in which case proteins like p53 and p21 can halt the cycle to either repair the damage or initiate apoptosis.