Diagram of Mitosis

This follows the page about the context of mitosis which states its position in the sequence of processes that, together, form the 'cell cycle' for somatic cells.

Definition: Mitosis is defined as the type of cell division by which a single cell divides in such a way as to produce two genetically identical "daughter cells". This is the method by which the body produces new cells for both growth and repair of aging or damaged tissues throughout the body - as opposed to for sexual reproduction (when meiosis applies).

Mitosis is the simplest of the two ways (mitosis and meiosis) in which the nucleus of a cell can divide - as part of a process of whole cell division. The four stages of mitosis (prophase, metaphase, anaphase and telophase) are shown and described below.

Mitosis (Nuclear Division)

0.

Interphase

Interphase is not part of mitosis but is included here as a reminder that interphase preceeds mitosis.
(Hence, it has the number 0.)

Chromatin is material in a cell nucleus consisting of DNA and protein. This is the substance that chromosomes are made from. It can be stained with dyes in order to watch the process of mitosis using a microscope.

1.

Above: Early Prophase

Above: Late Prophase

Prophase

  • Early in the prophase stage the chromatin fibres shorten into chromosomes that are visible under a light microscope. (Each prophase chromosome consists of a pair of identical double-stranded chromatids.)
  • Later in prophase, the nucleolus disappears, the nuclear envelope breaks down, and the two centrosomes begin to form the miotic spindle (which is an assembly of microtubules).
  • As the microtubules extend in length between the centrosomes, the centrosomes are pushed to opposite "poles" (extremes) of the cell.
  • Eventually, the spindle extends between two opposite poles of the cell.

2.

Metaphase

Metaphase is characterized by the "metaphase plate". This is a mid-point region within the cell that is formed/defined by the centromeres of the chromatid pairs aligning along the microtubules at the centre of the miotic spindle.

3.

Above: Early Anaphase

Above: Late Anaphase

Anaphase

  • The centromeres split seperating the two members of each chromatid pair - which then move to the opposite poles of the cell: When they are seperated the chromatids are called chromosomes.
  • As the chromosomes are pulled by the the microtubules during anaphase, they appear to be "V"-shaped because the centromeres lead the way, dragging the trailing arms of the chromosomes towards the pole/s.

4.

Telophase

  • Telophase begins after the chromosomal movement stops.
  • The identical sets of chromosomes - which are by this stage at opposite poles of the cell, uncoil and revert to the long, thin, thread-like chromatin form.
  • A new nuclear envelope forms around each chromatin mass.
  • Nucleoli appear.
  • Eventually the miotic spindle breaks-up.

0.

Interphase - see top of page

The cycle is about to start again ...

Interphase is not part of mitosis but is included here as a reminder that interphase preceeds mitosis.
(Hence, it has the number 0.)

 

Then the cytoplasm begins to divide around the two new nuclei - which is called Cytokinesis (Cytoplasmic Division). When cytokinesis is complete, interphase begins (see further up this page). This begins the next "cell cycle".


Go back to read about the context of mitosis or go on to read the page about cell division via meiosis.

What is Histology ?

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This is not medical, First Aid or other advice and is not to be used for diagnosis or treatment. Consult an expert in person. Care has been taken when compiling this page but accuracy cannot be guaranteed. This material is copyright.

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