We explain what mitosis is and the different phases of this form of reproduction. Also, what does meiosis consist of?
What is mitosis?
Mitosis is called the most common form of asexual reproduction of eukaryotic cells that is, those endowed 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, which is why it does not provide genetic variability except in the case of point mutations.
Mitosis is a common cellular process, which It occurs even between the cells of the human body and other multicellular animals, since it is the way to repair damaged tissue, or increase body size (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 damage or copying errors from occurring in the DNA during the replication process, especially in the initial phases, which leads to more or less dangerous mutations.
It must be considered that mitosis is a traumatic cellular process, that is, it forces the cell to undergo a series of changes and that interrupts its normal functioning for a period of 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, and which produces cells with many copies of the same chromosome in the same nucleus.
Phases of mitosis
Mitosis is a complex process that can be divided into phases, which are:
- Interface The first phase involves 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 everything before division.
- Prophase Immediately afterwards the envelope of the cell nucleus begins to break, as the centrosome also duplicates and each of the two resulting ones migrates towards a different end of the cell, to serve as polarity in the division, forming filamentous structures called microtubules that will serve to separate the chromosomes.
- Prometaphase The nuclear envelope dissolves and microtubules invade the space where the genetic material is, to begin 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 separate 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 one responding to a specific set of microtubules, in order to avoid repetitions.
- Anaphase It is the crucial stage of mitosis, as the two sets of chromosomes begin to move apart and make up two entire sets separately. 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 due to pressure.
- Telophase. Here the processes of prophase and prometaphase are reversed, as the microtubules continue to stretch and push the cell from the inside in two opposite directions. Each group of chromosomes recovers its nuclear envelope, from the fragments that remain of the original, and completes karyokinesis (nuclear division).
- Cytokinesis The event that culminates mitosis consists of the creation of a cleavage furrow in the common cytoplasm of the two new cells, right in the place where the chromosomes aligned (metaphase plate). The cytoplasm is thus strangled until the membrane allows the total separation and definitive birth of two daughter cells identical to the original mother.
Meiosis
Meiosis is a process that is sometimes similar to mitosis, but is distinguished from it by being a mode of sexual reproduction combinatorial, which introduces genetic variation and results in a new individual with a single genome, instead of two individuals that share a genome.
The sexual reproduction of humans 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 genetic load of the entire individual, and when combined with that of the other gamete (eggs and sperm), the entire DNA is restored, after passing some phases of random recomposition.
This reproduction method it is the most convenient for life since it does not produce clones of the parent, but rather a totally new individual, carrying fragments of the genome of each of its parents.
