Fundamental Processes - Overview of the Cell Cycle

Control of Cell Division

• Most cells have two major phases: mitosis and interphase often together referred to as the cell cycle
• For most tissues at any given time, only a few cells are in mitosis while the rest remain in interphase which is the period between divisions of the cytoplasm and is where a typical eukaryotic cell spends most of its life
• Some cells lose the capacity to divide altogether and stay in interphase indefinitely (for example in humans: nerve cells and muscle cells), while some divide regularly and others only occasionally

The Cell Cycle

Interphase consists of three sub-phases:

• G₁ is Gap 1 → the period just after mitosis and before the beginning of DNA synthesis
• S (synthesis) → which is the time when the cell’s DNA is replicated
• G₂ is Gap 2 → the time after S and prior to mitosis

Mitosis and cytokinesis are referred to as M-phase:

• the G₁→S transition commits the cell to enter another cell cycle