Final answer:
The tumor-suppressor protein p53 can activate genes involved in DNA repair, prevent the cell from completing the cell cycle, and initiate programmed cell death known as apoptosis when a cell has double-strand breaks in its DNA.
Step-by-step explanation:
The tumor-suppressor protein p53 can affect three processes when a cell has double-strand breaks in its DNA. Firstly, it activates genes involved with DNA repair to prevent mutations being passed on to daughter cells.
Secondly, it prevents the cell from completing the cell cycle, allowing time for DNA repair to occur.
Lastly, p53 can initiate programmed cell death known as apoptosis when DNA damage cannot be repaired.