Cell Division: Mitosis

Cells are the building blocks for all forms of life. The cells in your skin are different from the cells in a plant, but they are all cells. The basic parts of a cell are the nucleus and organelles. The nucleus is the control center of the cell and controls all the functions in the cell. Chromosomes and DNA are in the nucleus. The organelles are specialized to do certain tasks for the benefit of the whole cell. Just like the organs in your body, they have a special task.

Just like you grow, your cells grow, too. When a cell grows too big to be efficient, it divides into two cells. All of the organelles and the nucleus make copies of themselves and the cell divides. This process is called mitosis. Mitosis can be broken down into five different stages.

Interphase
Prophase
Metaphase
Anaphase
Telophase

Interphase: Interphase is the period between cell divisions. A cell spends most of its life in this phase. During interphase, the genetic material is in the form of chromatin. Chromatin is spread throughout the nucleus in a fine network of thin threads.
Before the actual cell division begins, the DNA in the chromatin makes copies of itself. The DNA does not separate yet; the copy is attached to the original. When the DNA replicates, mitosis is ready to begin.

Prophase: Prophase is the first actual phase of mitosis. The long threads of chromatin slowly shorten and become thicker. They are now visible as chromosomes. Each chromosome has two identical parts because the DNA is duplicated and both parts are still together. The membrane around the nucleus disappears in the cytoplasm. Also during prophase, a structure called a spindle begins to form. A spindle is shaped like a football and the ends are called poles. There are thin fibers that run between the poles of the spindle.

Metaphase: The chromosomes line up in the middle of the spindle. They line up side-by-side in a straight line. The chromosomes attach to the fibers at their midpoints.

Anaphase: The two identical halves of the chromosomes split apart during anaphase. They move away from each other toward the opposite poles of the spindle. When the chromosome halves reach the poles, anaphase is over. There is the same number of chromosomes at each pole of the spindle. This number is the same number a complete cell is supposed to have.

Telophase: In this phase, the chromosomes unwind and become chromatin once again. The spindle disappears, and a nuclear membrane forms around the bundle of chromatin. The cytoplasm divides in the middle of the cell. There are now two complete cells, each with the same number of chromosomes as the parent cell.

[Interphase] [Prophase] [Metaphase] [Anaphase] Telophase [Top]

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