The Steps of Mitosis

Mitosis is an incredible process with precise steps and regulation. Without mitosis, life would be impossible. However, the process can seem a bit complex.

A cell going through the six stages of mitosis

To begin, let’s explore the different stages of mitosis.

An artist's rendering of a cell in prophase, and a micrograph of a cell in prophase. The condensed chromosomes are clearly visible in both.

Prophase is the first stage of mitosis. In prophase,

  • chromosomes condense and become visible
  • spindle fibers emerge from the centrosomes
  • nuclear envelope breaks down
  • nucleolus disappears

An artist's rendering of a cell in prometaphase, and a micrograph of a cell in prometaphase. In both images, mitotic spindles are visible, and centrosomes are moving toward opposite poles.

Prometaphase is the second stage of mitosis. In prometaphase,

  • chromosomes continue to condense
  • kinetochores appear at the centromeres
  • mitotic spindle microtubules attach to kinetochores
  • centrosomes move toward opposite poles

An artist's rendering of a cell in metaphase, and a micrograph of a cell in metaphase. In both images, the mitotic spindles are clearly visible and chromosomes are lined up.

Metaphase is the third step in mitosis. In mitosis,

  • mitotic spindle is fully developed, centrosomes are at opposite poles of the cell
  • chromosomes are lined up at the metaphase plate
  • each sister chromatid is attached to a spindle fiber originating from opposite poles

An artist's rendering of a cell in anaphase, and a micrograph of a cell in anaphase.

Anaphase is the fourth step in mitosis. In anaphase,

  • cohesin proteins binding the sister chromatids together break down
  • sister chromatids (now called chromosomes) are pulled toward opposite poles
  • non-kinetochore spindle fibers lengthen, elongating the cell

An artist's rendering of a cell in telophase, and a micrograph of a cell in telophase.

Telophase is the fifth step in mitosis. In telophase,

  • chromosomes arrive at opposite poles and begin to decondenese
  • nuclear envelope material surrounds each set of chromosomes
  • the mitotic spindle breaks down

An artist's rendering of an animal cell undergoing cytokinesis, and a micrograph of a plant cell undergoing cytokinesis. In both, the two daughter cells can clearly be seen dividing.

Cytokinesis is the sixth and final step of mitosis. In cytokinesis,

  • Animal cells: a cleavage furrow separates the daughter cells
  • Plant cells: a cell plate separates the daughter cells

Mitosis

Now that we’ve reviewed each of the steps, let’s look at the cycle as a whole:

The cell cycle, with each step labelled. The six steps in order are prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis. Mitosis ends when two daughter cells are produced.

Mitosis: In Summary

In prophase, the nucleolus disappears and chromosomes condense and become visible. In prometaphase, kinetochores appear at the centromeres and mitotic spindle microtubules attach to kinetochores. In metaphase, chromosomes are lined up and each sister chromatid is attached to a spindle fiber. In anaphase, sister chromatids (now called chromosomes) are pulled toward opposite poles. In telophase, chromosomes arrive at opposite poles, and nuclear envelope material surrounds each set of chromosomes. Finally, in cytokenesis, the two daughter cells are separated.

Let’s take a quick quiz to review what we’ve just learned!

Practice Quiz

Which of the following options shows the correct order of the steps of mitosis?

  1. prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis.
  2. metaphase, prometaphase, prophase, anaphase, telophase, and cytokinesis.
  3. prophase, prometaphase, metaphase, telophase, anaphase, and cytokinesis.

What step of mitosis is shown here?

an artist's rendering of a cell. The nuclear envelope is breaking down and chromosomes are visible.

What step of mitosis is shown here?

The mitotic spindles are clearly visible and chromosomes are lined up.

Which step does the following passage describe?

The kinetochores appear at the centromeres, the mitotic spindle microtubules attach to kinetochores, and the centrosomes move toward opposite poles.

What occurs during anaphase?

  1. Each sister chromatid (or chromosome) is attached to a spindle fiber originating from opposite poles
  2. Sister chromatids (or chromosomes) are pulled toward opposite poles
  3. Sister chromatids (or chromosomes) arrive at opposite poles and begin to decondense

Which of the following is the correct order of events in mitosis?

  1. Sister chromatids line up at the metaphase plate. The kinetochore becomes attached to the mitotic spindle. The nucleus reforms and the cell divides. Cohesin proteins break down and the sister chromatids separate.
  2. The kinetochore becomes attached to the mitotic spindle. Cohesin proteins break down and the sister chromatids separate. Sister chromatids line up at the metaphase plate. The nucleus reforms and the cell divides.
  3. The kinetochore becomes attached to the cohesin proteins. Sister chromatids line up at the metaphase plate. The kinetochore breaks down and the sister chromatids separate. The nucleus reforms and the cell divides.
  4. The kinetochore becomes attached to the mitotic spindle. Sister chromatids line up at the metaphase plate. Cohesin proteins break down and the sister chromatids separate. The nucleus reforms and the cell divides.