What is the first thing that happens when a healthy cell detects damage to dna?

When a healthy cell detects damage to its DNA, it stops the cell cycle and tries to repair the damage. Healthy cells have phases that act as checkpoints to examine the internal and external conditions and decide whether to continue with the cell division. There are mechanisms and enzymes that are used to repair the DNA damage. If the damage is irreparable, in an effort to prevent the damaged DNA to pass on to the daughter cells, the cell may undergo programmed cell death.