Question

Checkpoints are pauses between phases of the cell cycle during which a cell determines whether or not it is ready to proceed to the next phase. For example, because a cell with damaged DNA can lead to cancer if it is allowed to divide, it usually arrests the cell cycle until the damage can be repaired. At which phase(s) of the cell cycle would a cell normally check for the integrity of its DNA?

Answer 1

A cell normally checks for the integrity of its DNA at the G1 checkpoint before DNA synthesis, at the G2 checkpoint before mitosis to ensure full replication and no DNA damage, and at the metaphase checkpoint to confirm proper chromatid attachment to the spindle apparatus.

Step-by-step explanation:

Cells in eukaryotic organisms have built-in safety measures called cell cycle checkpoints to ensure accurate division and duplication of the genetic material. These checkpoints are critical for preventing mutations that could lead to diseases such as cancer. A cell normally checks for the integrity of its DNA at several points during the cell cycle, specifically:

1. The G1 checkpoint near the end of G1, before entry into the S phase, where the cell decides whether it is ready for DNA synthesis.
2. The G2 checkpoint at the G2/M transition, which confirms whether all chromosomes have been replicated and that the replicated DNA is not damaged. This checkpoint is crucial to ensure that the cell's genetic information is intact before proceeding to mitosis.
3. The metaphase checkpoint during metaphase of mitosis, ensuring that all sister chromatids are properly attached to the spindle apparatus before separation.

The mechanisms that control these checkpoints involve proteins such as cyclins and cyclin-dependent kinases which work together to either halt or promote the cell cycle progression.