Phases of mitosis

Prophase - chromosomes condense

  • The chromosomes condense
  • The nucleolus disappears
  • The nuclear envelope disintegrates
  • The mitotic spindle begins to form

Prometaphase - chromosomes attach to the spindle filaments

  • The chromosomes attach to the spindle filaments and move to the equatorial plane of the cell.

Metaphase - chromosomes line up at the equator

  • Each chromosome is stabilized in the equatorial plane with two filaments that come from different poles.

Anaphase - chromatids diverge

  • The centromeres of the chromosomes are cleaved.
  • Each chromatid becomes an independent chromosome.
  • Former sister chromatids move to different poles of the cell.

Telophase - formation of nucleoli and nuclear envelope

  • Decondensation of the chromosomes
  • Resumption of synthetic processes in the cell
  • Formation of nucleoli and nuclear envelope
  • Destruction of the mitotic spindle
  • Doubling of the centrioles
  • Cytokinesis: division of the cytoplasm of the cell into two daughter cells.

Mitosis is division of the cell, when two daughter cells are genetically identical to the mother cell. Before mitosis, the chromosomes are duplicated. During mitosis they are distributed between daughter cells so that each receives one chromatid of each chromosome.

There are several phases in mitosis. However before, there is long interphase. Together mitosis and interphase consists the cell cycle. During interphase the cell grows, organelles are created, the synthesis processes are actively proceeding. In synthesis phase of interphase, DNA is replicated.

After chromatids duplicate, they remain connected in the centromere region. Thus, each chromosome consists of two chromatids.

In mitosis, there are usually (sometimes more) four main stages. These are prophase, metaphase, anaphase, telophase.

The first stage of mitosis is prophase. During it, chromosomes condense and take a compact form. Processes of RNA synthesis become impossible. The nucleoli disappear, so the ribosomes are also not formed and the synthetic processes in the cell are suspended. Centrioles diverge to the poles (to different ends) of the cell, the mitotic spindle begins to form.

Prometaphase is a phase, which not always singled out separately. The processes occurring in it can be attributed to the late prophase or early metaphase. During prometaphase, the chromosomes are in the cytoplasm and randomly move in the cell until their centromeres connect to the filaments of the mitotic spindle.

The filament is a microtubule constructed from tubulin protein. It grows by adding new tubulin subunits. So the chromosome moves away from the pole. The filament of the other pole also joins the chromosome and pushes it back.

The second phase of mitosis is metaphase. All chromosomes are located on the equatorial plane. Two filaments of spindle are attached to their centromeres. Metaphase is the longest stage of mitosis.

The third stage of mitosis is anaphase. During it, chromatids of each chromosome are separated from each other and move to different poles due to pulling filaments. Now microtubules are not built up, they are disassembled. Anaphase is a fast stage of mitosis. In this time the organelles of the cell also move to different poles approximately in equal amounts.

The forth stage of mitosis is telophase. Many processes are reverse prophase. Chromatids locate in poles region, they despiralise (decondense). On each pole, nuclear envelopes form around chromosomes. Nucleoli appear, RNA synthesis begin. The mitotic spindle begins to collapse. Further, the cytoplasm is divided. The process is called cytokinesis. In animal cells, this occurs due to the invagination of the membrane inside and the formation of a constriction. In plant cells, the membrane begins to form inside the equatorial plane and goes to the periphery.