Cell Cycle: Checkpoints in Cell Division

At which checkpoint in the cell cycle does a cell detect a problem with its DNA and determine that it should not be copied?

Answer:

The cell is at the G₁ checkpoint in the cell cycle when it detects a problem with its DNA and determines that it should not be copied.

During the cell cycle, there are several checkpoints that ensure the cell is ready to proceed with division. The G₁ checkpoint, also known as the restriction point, is the first major checkpoint in the cell cycle. At this checkpoint, the cell evaluates whether the conditions are favorable for cell division to occur.

When a cell detects a problem with its DNA at the G₁ checkpoint, such as an error that should not be copied, it will prevent further progression in the cell cycle. This is a crucial mechanism to ensure that damaged or mutated DNA is not passed on to new cells through division.

At the G₁ checkpoint, the cell also assesses its size, nutrient availability, and growth factors before committing to the next phase of the cell cycle. If the conditions are not optimal, the cell may enter a non-dividing state known as G₀ phase or undergo programmed cell death (apoptosis) to prevent further replication of damaged DNA.