Mitosis

What happens with mitosis?

The process of mitosis is understood to mean the simple division of the nucleus, at the end of which one cell results in two identical daughter cells. The function of mitosis is therefore the proliferation of cells.

In humans and animals virtually new cells are formed on a regular basis. Whether in growth, regeneration of injuries or the replacement of old cells, mitosis is responsible for the formation of new cells.

Mitosis is strictly distinguishable from meiosis, which reduces the number of chromosomes. See also: Comparison of mitosis and meiosis

Mitosis can be divided into the phases prophase, metaphase, anaphase and telophase:

Prophase

The chromosomes, consisting of two identical chromatid strands (in the picture the red X in the brown cell nucleus) shorten and condense by being unfolded in the cell nucleus. As a result, they are brought into a, necessary for mitosis, transportable form.

In the prometaphase, the surrounding nuclear envelope disintegrates and releases the chromosomes. In addition, the spindle apparatuses are formed at the edge of the cell. These consist of microtuboli and are later important for the transport of chromatids to the poles.

There is disagreement in science as to whether prometaphase is considered a separate phase or should be added to prophase. Regardless of how you decide, the prometaphase is mentioned here at least for the sake of completeness.

Metaphase

In the equatorial plane of the cell, the chromosomes arrange themselves. The spindle fibers (blue lines in the picture) now "dock" to the centromeres of the chromosomes. The centromere connects the two chromatids

Anaphase

The spindle-mounted spindle fibers shorten and provide a pulling action. This separates the chromosomes into their two chromatid strands and pulls them to opposite poles.

This means that each chromosome now has an identical chromatid strand at both poles.

Telophase

The chromatid strands now form a nuclear envelope at both poles. The chromosomes are unfolded back to their original shape. In addition, the division of the cell (cytokinesis) takes place in parallel, because there is only one cell with two nuclear envelopes (see right). The cytosyl (cell plasma) including the cell components is divided between the two daughter cells. Only in the context of interphase cell division is completed.

Interphase

Strictly speaking, the interphase does not belong to the actual mitosis. It describes the period between the last and the next cell division.

The two core shells that have now been formed contain only single-stranded chromatids. For a new mitosis, however, the chromosomes must again be double-stranded. This happens in the context of replication, so that afterwards each chromosome again consists of two identical chromatid strands. The process of mitosis can now start anew.

Summary

As part of mitosis, two cells become identical daughter cells

Mitosis has four phases: prophase, metaphase, anaphase and telophase. The interphase as well as the cytokinesis are not part of the mitosis