What is mitosis?
The most common form of asexual reproduction of eukaryotic cells is called mitosis, that is, those equipped with a nucleus where their complete genetic material resides. This process takes place when a single cell divides into two identical cells, endowed with the same DNA, so it does not provide genetic variability except in the case of specific mutations.
Mitosis is a common cellular process, which occurs even between the cells of the human body and other multicellular animals since it is the way to repair damaged tissue or to increase the size of the body (growth). The total reproduction of the individual, on the other hand, occurs through gametes and is called meiosis.
The primary task of mitosis is, of course, cell multiplication, but also the intact preservation of genetic information, through identical copies ( clones ). This does not prevent DNA damage or copy errors from occurring during the replication process, especially in the initial stages, which leads to more or less dangerous mutations.
It must be considered that mitosis is a traumatic cellular process, that is, that it forces the cell to undergo a series of changes, and that interrupts its normal functioning for some time.
Many single-celled organisms use mitosis to reproduce. It can also occur in the form of endomitosis, when a cell divides internally, without completely separating its cytoplasm and without dividing its nucleus, in a process also known as endoreplication, which produces cells with many copies of the same chromosome in the same core.
Phases of mitosis in order
In metaphase, the chromosomes are separated from the genetic material one by one.
Mitosis is a complex process that can be divided into phases, which are:
- Interface. The first phase supposes a momentary suspension of the cell’s tasks, while it dedicates its energies to duplicating its content: duplicating its DNA chain, duplicating its organelles, to have double of everything before division.
- Prophase. Then the envelope of the cell nucleus begins to break, as the centrosome also duplicates and each of the two resulting migrates towards a different end of the cell, to serve as a polarity in the division, forming filamentous structures called microtubules that will serve to separate the chromosomes.
- Prometaphase. The nuclear envelope dissolves and the microtubules invade the space where the genetic material is, to initiate the separation into two different sets. In this process, energy is consumed in the form of ATP.
- Metaphase. This is the checkpoint of mitosis, in which the chromosomes are separated from the genetic material one by one, lining up in the middle of the cell (equator). This phase does not end until all the chromosomes have detached and are aligned, each responding to a certain set of microtubules, to avoid repetitions.
- Anaphase. It is the crucial stage of mitosis, as the two chromosome sets begin to move apart and makeup two separate sets. This occurs thanks to the elongation of the microtubules that promote separation, pushing the genetic material and the centrosomes towards opposite poles of the cell, which begins to expand under pressure.
- Telophase. Here the processes of prophase and prometaphase are reversed, as the microtubules continue to stretch and push the cell from within in two opposite directions. Each group of chromosomes recovers its nuclear envelope, from the remaining fragments of the original, and karyokinesis (nuclear division) culminates.
- Cytokinesis The event that culminates in mitosis consists of the creation of an excision groove in the common cytoplasm of the two new cells, right in the place where the chromosomes lined up (metaphase plate). The cytoplasm is thus strangulated until the membrane allows the total separation and the definitive birth of two daughter cells identical to the original mother.
Meiosis requires the union of eggs and sperm.
Meiosis is a process at times similar to mitosis, but which differs from it in being a combinatorial, sexual mode of reproduction that introduces genetic variation and results in a new single genome individual, rather than two individuals that share a genome.
The sexual reproduction of the human being and other animals responds to this process, which requires the union of two gametes (instead of a single stem cell): cells that contain half of the individual’s genetic load, and that when put together with that of the other gamete (ovules and sperm), the entire DNA is restored, after passing some random recomposition phases.
This method of reproduction is the most convenient for life, since it does not produce clones of the parent, but a new individual, carrying fragments of the genome of each of its parents.
What is mitosis? phases of mitosis in order