Question

A gene that encodes a protein necessary for a cell to stop at checkpoints is an example of a(n) tumor-suppressor gene. growth factor. oncogene. angiogenesis inhibitor.

Answer 1

The right answer is a tumor-suppressor gene.

Tumor suppressor gene has a role in the cell cycle to stop it at checkpoints, in order to verify that everything is okay in the cell and there's no DNA damage, if there's a DNA lesion, the cell must repair it before resuming its cycle. If there's no problem with the genetic material, the cell will proceed its cycle.
If these tumor suppressor gene is unfunctionnal, mutations will happen during the cell cycle withou being repaired, so it lead to a formation of tumors, and that is why it is called so.

These checkpoints happen specifically in G1 and G2 phases.