Mitosis is the stage in the eukaryotic cell cycle in which the cell nucleus divides in half, with each half receiving identical genetic material.

A cell's chromosomes are replicated before mitosis, during the S phase of interphase.

After replication, each of the two identical copies of chromosomes is known as a chromatid.

The two identical chromatids (known as sister chromatids) in a pair are joined at a spot known as the centromere.

Mitosis takes place after interphase.

Mitosis differs from meiosis, the process by which gametes (sex cells) are formed.

In meiosis, the number of chromosomes in each new cell is halved, while in mitosis, each daughter cell retains the same number of chromosomes as the parent cell.

The four stages of mitosis are

  1. Prophase
  2. Metaphase
  3. Anaphase
  4. Telophase


During prophase, chromatin - which is made up of protein and DNA - in the nucleus condenses and coils to form chromosomes.


During metaphase, the nuclear membrane (nuclear envelope) breaks down and the chromosomes fill the cell.

A spindle becomes present during metaphase.

The spindle is shaped like an ellipsoid, wide in the middle and tapered at the ends.

The ends of a spindle are known as spindle poles.

The spindle contains microtubules that began and end at the poles.

During metaphase, some of the microtubules become attached to chromatids on places on the centromere that are known as kinetochores.

This causes the chromatids to line up in a plane that passes throught the middle of the cell.

In a few eukaryotes, such as fungi and algae, the nuclear membrane stays intact throughout mitosis.

These organisms undergo a process called closed mitosis, in which the spindle microtubules penetrate the nuclear membrane, or the entire spindle forms within the nucleus.


During anaphase, the spindle microtubules shorten, which causes the sister chromatids separate.

Each chromatid moves to the spindle pole closest to it.

Once the sister chromatids have separated, they are known as daughter chromosomes.

Telophase and CytokinesisTelophase

During telophase, a nuclear membrane forms around each set of daughter chromosomes.

The chromosomes uncoil and the spindle microtubules disappear.

Telophase is usually followed by cytokinesis, in which the entire cell divides.