Mitosis is the process that produces two genetically identical cells from a single parent cell. It takes roughly 30 to 60 minutes to complete in human cells and is responsible for nearly all the new cells your body creates throughout your life, from growing taller as a child to healing a cut on your skin.
If you’re comparing it to meiosis (the other major type of cell division), the key distinction is straightforward: mitosis copies everything equally so both daughter cells match the original, while meiosis shuffles DNA and cuts the chromosome count in half to produce sex cells like sperm and eggs. Below is a closer look at how mitosis actually works, what keeps it accurate, and where it fits alongside other forms of cell division.
How Mitosis Produces Two Identical Cells
Before a cell divides, it first copies all of its DNA during a preparatory period called the S phase. Each chromosome is duplicated into two connected halves called sister chromatids. Once that copying is finished, the cell enters mitosis itself, which unfolds in four continuous stages.
- Prophase: The copied chromosomes condense into compact, visible structures. A scaffold of protein fibers called the mitotic spindle begins forming between two opposite poles of the cell.
- Metaphase: The chromosomes line up along the cell’s midpoint. Spindle fibers attach to each chromosome so that one fiber connects each sister chromatid to an opposite pole, placing them under tension.
- Anaphase: The sister chromatids are pulled apart toward opposite ends of the cell. The nucleus stretches from a sphere into an elongated dumbbell shape as the two identical sets of chromosomes move away from each other.
- Telophase: A new nuclear envelope forms around each set of chromosomes, and the chromosomes begin to relax back into their less compact form.
After the nucleus has divided, the cell’s cytoplasm splits in a step called cytokinesis. In animal cells, a ring of proteins pinches the membrane inward like a drawstring until the cell is squeezed into two. Plant cells handle this differently: small membrane-bound packages fuse together along the midline to build a new cell wall from the inside out. Either way, the result is two separate cells, each with a complete and matching copy of the original genome.
What Keeps the Copies Accurate
Copying 6 billion DNA letters (the size of the human genome) is not error-free on the first pass. The enzymes responsible for DNA replication make mistakes roughly once every 10,000 to 100,000 letters, which means each round of copying initially generates somewhere between 100,000 and 1,000,000 errors. That sounds alarming, but the cell runs multiple layers of quality control that catch and fix the vast majority of those mistakes before division ever begins.
The cell cycle has a series of built-in checkpoints that act like security gates. At the G1 checkpoint, the cell verifies that it has grown large enough and that its DNA is undamaged before committing to replication. During replication itself, an intra-S-phase checkpoint pauses the process if the copying machinery hits a blockage, keeping it in place so work can resume once the problem is cleared. A G2 checkpoint then confirms that replication is fully finished and the DNA is intact before the cell is allowed to enter mitosis. If damage is detected at any of these stages, the cell halts and activates repair pathways.
One final checkpoint operates during mitosis itself: the spindle checkpoint. This mechanism prevents the cell from pulling chromosomes apart until every single chromosome is properly attached to spindle fibers from both poles and under the right amount of tension. A chromosome connected to only one pole, or attached incorrectly, will stall the entire process. This ensures each daughter cell ends up with exactly the right number of chromosomes rather than gaining or losing one.
Why Your Body Needs Identical Cells
Multicellular organisms depend on mitosis for two major purposes: growth and repair. A fertilized egg divides by mitosis again and again to build a full human body containing trillions of cells. After growth is complete, mitosis continues in tissues that experience constant wear. The lining of your intestines replaces itself roughly every three to five days, and your skin continuously generates new cells to replace those shed from the surface. Blood cell precursors in bone marrow divide rapidly to maintain the supply of red and white blood cells.
Because every cell produced by mitosis carries the same DNA as the original, the genetic instructions stay consistent across tissues. A new skin cell has the same genome as a new liver cell. What makes them behave differently is not their DNA content but which genes each cell type switches on or off.
When Identical DNA Doesn’t Mean Identical Cells
There is an important nuance: mitosis always produces genetically identical daughter cells, but those cells don’t always end up with the same fate. Stem cells regularly perform a variation called asymmetric division. During this process, certain signaling molecules and regulatory proteins inside the cell are distributed unevenly before division. Both daughter cells receive the same DNA, but one inherits the molecular signals that keep it as a stem cell while the other inherits signals that push it to specialize. This is how tissues like the blood, gut lining, and skin maintain a reserve of stem cells while still producing the differentiated cells they need.
How Mitosis Compares to Other Division Types
Mitosis vs. Meiosis
Meiosis is a fundamentally different process with a different goal. It divides one cell into four daughter cells, each containing half the original number of chromosomes. During meiosis, matching chromosomes from your mother and father swap segments of DNA in a step called crossing over, creating new genetic combinations that didn’t exist in either parent. The result is four genetically unique sex cells. Mitosis, by contrast, skips all of that shuffling and simply copies the full chromosome set into two matching cells.
Mitosis vs. Binary Fission
Bacteria and other prokaryotes don’t have nuclei, so they don’t undergo mitosis. Instead, they reproduce through binary fission, where the cell copies its single circular chromosome and splits down the middle. Each resulting cell gets one old end (pole) from the original and one newly formed end. Like mitosis, binary fission produces two genetically identical offspring, but the machinery is simpler because there are no spindle fibers, no condensed chromosomes to sort, and far less DNA to manage. Binary fission is also faster, allowing some bacteria to divide every 20 minutes under ideal conditions.