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genetics & heredity
Cell Division and Mitosis
When an organism grows, the total number of cells in an organism increases. Even in organisms that are no longer growing, cells are constantly dying and being replaced. Where do these new cells come from? CELL DIVISION. With cell division, one cell divides into two cells. Two cells can divide to create four cells, and then each of the four cells can divide to create eight cells, and so on. So an entire organism can grow from one cell alone.
The Cell Cycle
Each cell naturally goes through a life cycle. There are many phases of the cell cycle. One of these phases is when the cell divides, a process called MITOSIS. Mitosis is cell division that produces identical cells. In cell division, the nucleus is divided. Each DAUGHTER CELL is identical to the original parent cell. (The original PARENT CELL no longer exists at the end of mitosis.)
The other phases of a cell cycle make up the period where a typical cell spends the most time. These three phases together are called INTERPHASE. During interphase, a cell grows and duplicates its chromosomes (structures that contain all of the cell's DNA) and organelles in preparation for mitosis. The nuclei of the daughter calls will have the same number and type of chromosomes. One complete cell cycle is the time from one cell division to the next. Different cells have cycles of different lengths. |