The cell is a complex marvel of nature. Not only do complicated metabolic processes take place in it, it is also capable of dividing. Cell division is also important in this context.
You can find out more about cell division in the article of the same name!
Before a cell can divide completely, its nucleus must divide. This process is also known as mitosis.
Mitosis, or nuclear division, is a fundamental process in biology that describes the division of the cell nucleus in eukaryotic cells. The result is two daughter nuclei whose genome is identical. Subsequent to mitosis, the entire cell usually divides into two genetically identical daughter cells.
Since two genetically identical daughter cells develop from a mother cell during mitosis, nuclear division is an important process for the growth and regeneration of the organism. Unlike meiosis, it does not contribute to genetic diversity because the daughter cells are genetically identical.
Mitosis – 4 phases
You can divide mitosis into four phases:
- prophase
- metaphase
- anaphase
- telophase
However, mitosis does not stand alone. It is integrated into the so-called cell cycle and is M phase designated.
Figure 1: Cell cycle Source: spekter.de
If you want to know more about the cell cycle, you can check out the article on the subject.
The prophase of mitosis
Mitosis begins with prophase. In this phase, the chromosomes contract so much (spiralization) that the sister chromatids become visible. The paired centrioles separate.
The spindle apparatus forms between the centrioles. The individual spindle fibers that make up the apparatus consist of microtubules.
The process in plant cells is somewhat different. Since these do not have centrioles, the spindle apparatus is formed from the nuclear membrane.
The nucleus and the nuclear membrane then dissolve.
Figure 2: Prophase of mitosis Source: wikipedia.de
You can learn more about prophase in the related article on .
The metaphase of mitosis
In the metaphase, both the nucleus and the nuclear membrane have completely dissolved. The chromosomes are compressed as much as possible and easily visible as compact structures. This typical chromosome form is the so-called mode of transport.
The chromosomes are lined up in the so-called equatorial plane between the two «poles» of the spindle apparatus. The spindle fibers attach in the middle of the chromosomes. The area is also called centromere and is the junction between the two sister chromatids.
Starting from the two poles of the spindle apparatus, one spindle fiber each binds to the centromere of a chromosome.
Figure 3: Metaphase of mitosis Source: wikipedia.de
If you want to know more about this phase, check out the Metaphase article!
The anaphase of mitosis
During anaphase, the spindle fibers that attached to the chromosomes during metaphase shorten. This compression causes the chromatids of the chromosomes lined up in the equatorial plane to be pulled apart. The now separated chromatids migrate to the poles of the spindle apparatus.
Figure 4: Anaphase of mitosis Source: wikipedia.de
There is also a more detailed explanation of this phase in the article «Anaphase».
The telophase of mitosis
Once the chromatids have arrived at the respective poles, they begin to coil up again – their degree of compression decreases. The spindle fibers detach from the centromere of the chromatids and the whole apparatus is regressed. A new nuclear membrane forms.
Figure 5: Telophase of mitosis Source: wikipedia.com
Subsequent to the actual mitosis, cell division/cytokinesis occurs. The cell constricts in the middle and thus divides into two genetically identical daughter cells.
Differences between meiosis and mitosis
As you read above, unlike meiosis, mitosis does not contribute to genetic diversity because recombination does not occur.
The term recombination describes the redistribution of genetic material during meiotic division and is an important evolutionary factor. The recombination can be intrachromosomal, in the form of crossing overas well as interchromosomally (random distribution of the chromosomes to both cell poles in anaphase 1).
Mitosis takes place in all growing cells, i.e. there where a change in the genetic material is unfavorable. The daughter cells that arise after mitosis and subsequent cytokinesis are genetically completely identical.
Meiosis, on the other hand, takes place in humans only in the sex cells. Here there is a fundamental difference to mitosis. It is not the chromatids of the cells that are separated during meiosis, but the intact, homologous chromosomes. Since one chromosome comes from our mother and one from our father in our genome, they are not identical. After meiosis, daughter cells are formed that differ from each other.
Other differences between mitosis and meiosis are listed for you in the following table.
Comparative CriteriaMitosisMeiosisfunctionProliferation of body cells Production of germ / sex cellslocationWhere cells are renewed or needed for growthIn the gonadsIn women: ovariesIn men: testiclesprocessruns in four phases:runs in eight phases:recombinationNo YesresultTwo daughter cells with a diploid chromosome set (2n), which are genetically identical. Four daughter cells with a haploid chromosome set (1n), which are genetically different
Mitosis – The most important thing
- Mitosis describes the division of the cell nucleus in eukaryotic cells – two genetically identical daughter cells with a diploid set of chromosomes are formed.
- Mitosis is used for cell renewal and growth.
- The division of the cell nucleus takes place in the cell cycle after the interphase and is itself divided into four phases:
- Mitosis occurs where cells are renewed or needed for growth.
- Unlike meiosis, mitosis does not contribute to genetic diversity since recombination does not occur.