Question

During the cell cycle, there are checkpoints. The best way to define a checkpoint is:

a. A phase where cells rest
b. A point where DNA is replicated
c. A regulatory point for cell progression
d. A phase where cells divide

Answer 1

Checkpoints during the cell cycle are regulatory points where the cell assesses whether it can safely progress to the next phase. They occur at three main stages: G1, S (for DNA replication), and mitosis. Proteins like cyclins and CDKs help regulate this progression. Therefore, the correct option is C.

Step-by-step explanation:

During the cell cycle, checkpoints serve as regulatory points for cell progression. These checkpoints are critical control mechanisms ensuring that a cell does not advance to the next stage until it is ready. In eukaryotic cell cycles, these checkpoints are present near the end of G1, at the G2/M transition, and during metaphase.

The three main cell cycle checkpoints include:

The G1 checkpoint, which assesses whether a cell is ready for DNA synthesis and division based on size and other factors.

The S checkpoint (DNA synthesis checkpoint) ensures DNA has been correctly replicated.

The mitosis checkpoint checks that all chromosomes are properly aligned before cell division proceeds.

Proteins such as cyclins and cyclin-dependent kinases (CDKs) are crucial for advancing past these checkpoints. They evaluate conditions within the cell and provide 'stop' or 'go' signals to regulate the cycle. Therefore, the correct answer is c. A regulatory point for cell progression.