Answer:
1. C. These proteins prevent the cell cycle from progressing if damaged DNA is detected.
2. C. G2
Explanation:
1. All other choices apply uniquely to DNA repair enzymes (i.e. not to DNA checkpoint proteins).
2. Go doesn't contain any critical DNA damage checkpts. because it's not even an official part of the cell cycle; it's simply a phase in which cells are arrested. G1 doesn't contain any critical DNA damage checkpts. because it's before DNA is replicated. G2 is right after S phase when the DNA is replicated; thus, it contains critical DNA damage checkpts.