The cell cycle is a repeating series of events that includes growth, DNA synthesis, and cell division. The cycle is more complicated in eukaryotic than prokaryotic cells.
In a eukaryotic cell, the cell cycle has two major phases: mitotic phase and interphase. During mitotic phase, first the nucleus and then the cytoplasm divide. During interphase, the cell grows, performs routine life processes, and prepares to divide.
The cell cycle is controlled mainly by regulatory proteins that signal the cell to either start or delay the next phase of the cycle. They ensure that the cell completes the previous phase before moving on. There are a number of main checkpoints in the regulation of the cell cycle.
Cancer is a disease that occurs when the cell cycle is no longer regulated, often because the cell's DNA has become damaged. Cancerous cells grow out of control and may form a mass of abnormal cells called a tumor.
The cell division phase of the cell cycle in a eukaryotic cell occurs in two major steps: mitosis — when the nucleus divides — and cytokinesis, when the cytoplasm divides and two daughter cells form.