Mitosis

Mitosis is a type of the cell division. Before the mitosis starts it is necessary to replicate the chromosomes. The parts which are created during the replication are called "sisters chromatids". Later, they are separate by the mitotic spindle. Whole process takes about 160 minutes.

Mitosis has several phases that take place one after the other. They are called prophase, prometaphase, metaphase, anaphase and telophase.

Prophase

 * Chromosomes are the most condensed.
 * They look like we know them from the karyotype.
 * The mitotic spindle is creating outside the cell.
 * The movement of the centrosomes is caused by the interaction of proteins and microtubules.
 * Time: 90 minutes



Prometaphase

 * Cell is losing its nuclear membrane and chromosomes bind to the mitotic spindle.
 * Chromosomes are binding by the microtubules and proteins complexes called kinetochors. These proteins are located in the centromeres.
 * Microtubules are formed from the nucleat membrane.
 * Each sister chromatid has its own kinetochor (so there are two kinetochors on one chromosome).



Metaphase

 * All chromosomes going to the equatorial line.
 * The movement is caused by creating and destroying of the proteins which form the microtubules – this process is called "dynamic instability".
 * Every failure of the connecting leads to incorrect dividing of the chromatids and some chromosomal abnormality.
 * Time: 20 minutes



Anaphase

 * The sisters chromatids are divided by the proteolytic enzymes.
 * Each of them is transfered to the opposite part of the cell – it is caused by the depolymeration of the microtubules
 * Sister chromatid becomes the daughter chromosome.
 * Time: 10 minutes



Telophase

 * The nuclear membrane occurs again.
 * The condensed chromosomes change into their interphase state.
 * The transcription can continue.
 * From one parent nucleus two daughter nuclei are created.
 * Time: 45 minutes

Multinucleated Cells

 * Cell´s nuclei divided but the cytoplasma didn´t. The cells look giant and have several nuclei. E.g. xanthoma

Syntitial cells

 * Several cells fuse together.

Increased Rate

 * Typical in tumours – e.g. sarcoma or Hodgkin Lymphoma

Damage by the External Influences

 * 1) during mitosis – we can find multipolar spindle;
 * 2) in the resting cells – fragmentation of the chromosomes or forming of the micronuclei.

Related articles

 * Replication
 * Karyotype
 * Nondisjunction