Definition · Plain-language
Mitosis
Mitosis is the type of cell division that produces two genetically identical cells, used for growth, repair and replacing worn-out cells.
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Cell division for growth and repair
Mitosis is how a cell divides to make two identical copies of itself. It is the everyday cell division that lets a single fertilised egg grow into a whole organism, heals a cut by replacing damaged cells, and constantly renews tissues such as skin and the lining of the gut. Both new cells, called daughter cells, are genetically identical to the original and to each other. Some organisms also use mitosis for asexual reproduction, producing offspring that are exact genetic copies — clones — of the parent.
Copying the DNA first
Before a cell can divide, it must make a complete copy of its DNA so that each daughter cell ends up with a full set of chromosomes. This copying happens during a stage before mitosis. Then, during mitosis itself, the duplicated chromosomes are lined up and pulled apart so that one copy of each goes to each end of the cell. Finally the cell splits in two. Because the DNA was copied exactly first, both daughter cells receive identical genetic information.
Keeping the chromosome number the same
A key feature of mitosis is that the chromosome number stays the same. A human cell with 46 chromosomes divides into two cells that each also have 46. This is essential for growth and repair, where every new cell must be a faithful copy. It is the opposite of meiosis, which halves the chromosome number to make sex cells. Because mitosis copies cells exactly, it does not create genetic variation — all the cells it produces are clones of the original.
Key facts
At a glance
- Definition: cell division that makes two identical daughter cells
- Cells made: two, genetically identical to the parent
- Chromosomes: stay the same (e.g. 46 to 46 in humans)
- Used for: growth, repair, replacing cells, asexual reproduction
- First step: the DNA is copied before division
- Variation: none — the new cells are clones
Common misconceptions
What people often get wrong
Often heard: Mitosis produces cells with half the number of chromosomes.
Actually: That is meiosis. Mitosis keeps the chromosome number the same: a cell with 46 chromosomes makes two cells with 46 each. Halving the number is the job of meiosis, which makes sex cells.
Often heard: Mitosis creates genetic variation between the new cells.
Actually: Mitosis makes genetically identical copies, so it creates no new variation. The two daughter cells are clones of the parent. Genetic variation comes from meiosis and from sexual reproduction, not mitosis.
Often heard: Mitosis only happens while an organism is still growing.
Actually: Mitosis continues throughout life. Even in adults it constantly repairs injuries and replaces worn-out cells, such as skin and blood cells. Growth is only one of its roles.
Going deeper
