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Cell Cycle

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What is a cell's life like?

The eukaryotic cell spends most of its "life" in interphase, which can be divided into the three phases, G1, S and G2. During interphase, the cell does what it is supposed to do. 

The Cell Cycle

Cell division is just one of several stages that a cell goes through during its lifetime. The cell cycle is a repeating series of events that include growth, DNA synthesis, and cell division

The Eukaryotic Cell Cycle

The Figure below represents the cell cycle of a eukaryotic cell. As you can see, the eukaryotic cell cycle has several phases. Three phases (G1, S, and G2) are generally grouped together as interphase . During interphase, the cell grows, performs routine life processes, and prepares to divide.  The  mitotic phase  (M) actually includes both mitosis and cytokinesis. This is when the nucleus and then the cytoplasm divide.

The Eukaryotic Cell Cycle. This diagram represents the cell cycle in eukaryotes. The G1, S, and G2 phases make up interphase (I). The M phase includes mitosis and cytokinesis. After the M phase, two cells result.

Interphase

Interphase of the eukaryotic cell cycle can be subdivided into the following three phases, which are represented in Figure above :

  • Growth Phase 1 (G1): during this phase, the cell grows rapidly.  A cell typically spends most of its life in this phase. 
  • Synthesis Phase (S): during this phase, the cell’s DNA is copied in the process of DNA replication .
  • Growth Phase 2 (G2): during this phase, the cell makes final preparations to divide. For example, it makes additional proteins and organelles

Control of the Cell Cycle

If the cell cycle occurred without regulation, cells might go from one phase to the next before they were ready. What controls the cell cycle? How does the cell know when to grow, synthesize DNA, and divide? The cell cycle is controlled mainly by proteins. These proteins control the cycle by signaling 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. 

Cancer is a disease that occurs when the cell cycle is no longer regulated. This may happen because a cell’s DNA becomes damaged. Damage can occur due to exposure to hazards such as radiation or toxic chemicals. Cancerous cells generally divide much faster than normal cells. They may form a mass of abnormal cells called a tumor . The rapidly dividing cells take up nutrients and space that normal cells need. This can damage tissues and organs and eventually lead to death. Cancer is a form of out of control Mitosis. 

These cells are cancer cells, growing out of control and forming a tumor.

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