Question

In general, what is the purpose of a checkpoint in the cell cycle?

Answer 1

In order to control, is cell ready to go to division or not.

Explanation:

This check point is the start of the phase called G0 phase. Cell may stack this point because of abnormalities that are valuable for division.

Nerve cells cannot divide beause of their unlimited G0 phase.

Muscle cells are also stack in G0 phase. Because of that they can not totally divide. However, they are able to make nucleic division. And also they can divide their mitochondria with their nucleus. As a result of that and energy need, muscle cell mostly have many mitochondria in their inside.