A variety of genes are involved in the control of cell growth and division. The cell replicates itself in an organized, step-by-step fashion known as the cell cycle. Tight regulation of this process ensures that a dividing cell’s DNA is copied properly, any errors in the DNA are repaired, and each daughter cell receives a full set of chromosomes. The cell cycle has checkpoints (also called restriction points), which allow certain genes to check for problems and halt the cycle for repairs if something goes wrong.

If a cell has an error in its DNA that cannot be repaired, it may undergo self-destruction (apoptosis). Apoptosis is a common process throughout life that helps the body get rid of cells that no longer work or that it doesn’t need. Cells that undergo apoptosis break apart and are recycled by a type of white blood cell called a macrophage. Apoptosis protects the body by removing genetically damaged cells that could lead to cancer, and it plays an important role in the development of the embryo and the maintenance of adult tissues.

Disruption of normal regulation of the cell cycle can lead to diseases such as cancer. When the cell cycle proceeds without control, cells can divide without order and accumulate genetic errors that can lead to a cancerous tumor.