by N. David

Created on: December 31, 2009

The cell is the basic unit of all life. For an organism to grow and reproduce, new cells must come into being. This happens through a process called cell division, wherein one cell becomes two or more cells.

In prokaryotes, or simple organisms such as bacteria, cells divide using a process known as binary fission. In eukaryotes, or more advanced, multi-celled organisms such as plants and animals, the cell division process is more complex. Eukaryotes contain two types of cell, somatic cells and gametes.

Somatic cells make up the body of an organism. Internal organs, skin, connective tissue, blood and bones are all made up of somatic cells. Gametes are reproductive cells, such as human sperm cells and eggs. Somatic cells and gametes each use a different method of cell division.

Mitosis

Mitosis is the process by which somatic cells divide. As an organism grows to maturity, and as it repairs wounds and other damage, it does so using somatic cells. It is beyond the scope of this article to describe mitosis in detail, but here is a brief overview.

For cell division to occur, the chromosomes containing the organism's genetic material must first be duplicated. This occurs within the cell's nucleus, where the chromosomes are stored. The process in which chromosomes are duplicated is called interphase. Interphase is not part of the mitosis process, but it must occur before mitosis can take place.

Following interphase, the process of mitosis begins. The membrane of the nucleus dissolves and the chromosomes are separated, creating two identical sets of genetic material. A new nucleus then forms around each set of chromosomes, completing mitosis.

Following mitosis, a separate process called cytokinesis physically divides the cell into two separate cells. All somatic cells contain the complete genetic code of the organism to which they belong. When somatic cells divide, each new cell is a somatic cell that is genetically identical to the original.

Meiosis

Gametes are created through a process called meiosis. Meiosis takes place within the sex organs. In this process a cell doesn't divide into two genetically identical cells, as in mitosis. In meiosis, a cell divides into four cells, each containing only half of the organism's genetic sequence.

In sexual reproduction, two gametes combine to form a new cell, called a zygote. The zygote contains all the genetic material needed to develop into a new organism. If each gamete contained a complete set of genetic material, the zygote

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