raren 15. The cell cycle has some checkpoints to make sure things are proceeding correctly. List the 3 checkpoints: (Slide 17) a. __ b. __ c. __

## Step 1<br />The cell cycle is a series of events that cells undergo as they divide and grow. It consists of four main phases: G1, S, G2, and M. The cell cycle is regulated by several checkpoints to ensure that the cell is ready to proceed to the next phase.<br /><br />## Step 2<br />The first checkpoint is the G1 checkpoint, also known as the restriction point. This checkpoint occurs at the end of the G1 phase, before the cell enters the S phase. The cell checks for nutrients, growth factors, and DNA damage. If the conditions are not favorable, the cell will enter a resting state called G0.<br /><br />## Step 3<br />The second checkpoint is the G2 checkpoint. This checkpoint occurs at the end of the G2 phase, before the cell enters the M phase. The cell checks for DNA damage and ensures that all DNA has been replicated correctly.<br /><br />## Step 4<br />The third checkpoint is the M checkpoint, also known as the spindle checkpoint. This checkpoint occurs during the M phase, specifically during metaphase. The cell checks to ensure that all chromosomes are attached to the spindle fibers and that the chromosomes are aligned correctly at the metaphase plate.