A&P Discussion

The cell cycle is important as old cells get damaged and have to be replaced with new cells for the functioning of the body. If new cells are not formed the human body will stop working within a few minutes. The cell cycle is defined as an orderly sequence of events in which a somatic cell duplicates its contents and divides in two. When a cell reproduces, it must replicate all its chromosomes to pass its genes to the next generation of cells. The cell cycle consists of two major periods: interphase, when a cell is not dividing, and the mitotic phase, when a cell is dividing. During interphase the cell replicates its DNA. Interphase is a stage of high metabolic activity. Interphase has three phases: G1, S, and G2. The G1 phase is the interval between the mitotic phase and the S phase. During this phase the cell is active. It replicates most of its organelles and cytosolic components but not its DNA. The replication of centrosomes also begins in the G1 phase. For a cell with a total cell cycle time of 24 hours, G1 lasts 8 to 10 hours. Cells that remain in G1 for a very long time are destined to divide again in G0 phase. Most nerve and muscle cells are in this phase. Once a cell enters the S phase, it is committed to go through the rest of the cycle. The S phase last about 8 hours. During the S phase, DNA replication occurs. As a result, the two identical cells formed during cell division later in the cycle will have the same genetic material. The G2 phase last about 4-6 hours. During G2, cell growth continues, enzymes and other proteins are synthesized in preparation for cell division, and the replication of centrosomes is completed. The mitotic phase of the cell cycle, which results in the formation of two new cells, consists of a nuclear division, which is called mitosis, and a cytoplasmic division, which is called cytokinesis, to form two identical cells. The process of mitosis results in the exact partitioning of genetic information. During prophase, the