Differences between mitosis and meiosis

These two types of cell division cause a zygote to become an organism.

The human body is made up of 37 trillion cells. It is surprising that this immense number originates from a single cell that is conceived during fertilization. This is made possible by the ability of cells to self-reproduce, a process that involves dividing themselves in two. Gradually, the aforementioned quantity is reached, forming the different organs and cell types.

Now, there are two basic mechanisms by which cells can reproduce themselves: mitosis and meiosis. Below we will see the differences between mitosis and meiosis. the differences between mitosis and meiosis and their characteristics..

Mitosis and meiosis

We have seen that little by little, a few cells can give rise to an entire organism, whether it is a human being or a huge whale. In the case of the human being we are dealing with diploid eukaryotic cells.that is to say, they have one pair per chromosome.

The chromosome structure is the most compact and condensed form that DNA can have together with structural proteins. The human genome is made up of 23 pairs of chromosomes (23x2). This is an important fact to know one of the main differences between mitosis and meiosis, the two types of cell division that exist.

The eukaryotic cell cycle

Cells follow a series of sequential patterns for their division. This sequence is called the cell cycle, and consists of four coordinated processes: cell growth, DNA replication, distribution of duplicated chromosomes, and cell division.. This cycle differs at some points between prokaryotic (bacteria) or eukaryotic cells, and even within eukaryotes there are differences, for example between plant and animal cells.

The cell cycle in eukaryotes is divided into four stages: G1 phase, S phase, G2 phase (all of them are grouped in the interphase), G0 phase and M phase (Mitosis or Meiosis).

1. Interphase

This group of stages is intended to prepare the cell for its imminent splitting in two.following the following phases:

• Phase G1 (Gap1)corresponds to the gap between a successful division and the beginning of the replication of the genetic content. During this phase, the cell is in constant growth.
• S phase (Synthesis)is when DNA replication takes place, ending with an identical duplication of the genetic content. In addition, the chromosomes are formed with the more familiar silhouette (X-shaped).
• G2 phase (Gap2)Interphase: cell growth continues, as well as the synthesis of structural proteins that will be used during cell division.

Throughout interphase, there are several checkpoints to verify that the process is being carried out correctly and that there is no error (e.g., that there is no mismatch). If there are any problems, the process is stopped and a solution is sought, since cell division is a vitally important process; everything must go well.

2. G0 phase

Cell proliferation is lost when the cells become specialized so that the growth of the organism is not so that the growth of the organism is not infinite. This is possible because the cells enter a resting stage called G0 phase, where they remain metabolically active but show neither cell growth nor replication of the genetic content, i.e. they do not continue in the cell cycle.

3. M phase

It is in this phase that cell division takes place and either mitosis or meiosis either mitosis or meiosis takes place..

Differences between mitosis and meiosis

In the division phase is when either mitosis or meiosis occurs.

Mitosis

It is the typical cell division of a cell giving rise to two copies. As with the cycle, mitosis has also traditionally been divided into different stages: prophase, metaphase, anaphase and telophase. Although for a simpler understanding, I will describe the process in general rather than by each stage.

At the beginning of mitosis, the genetic content is condensed into the 23 pairs of chromosomes that make up the human genome. that make up the human genome. At this point, the chromosomes are duplicated and form the typical X-image of chromosomes (each side is a copy), joined in the middle by a protein structure known as the centromere. The nuclear membrane enclosing the DNA is degraded to make the genetic content accessible.

During the G2 phase, various structural proteins have been synthesized, some of them doubly. These are called centrosomeswhich are each positioned at opposite poles of the cell.

From the centrosomes extend the microtubules, the protein filaments that make up the mitotic spindle and which attach to the centromere of the chromosome, to stretch one of the copies to one of the sides, breaking the X structure.breaking the X-shape structure.

Once on each side, the nuclear envelope is re-formed to enclose the genetic content, while the cell membrane is strangulated to generate two cells. The result of mitosis is two diploid sister cellsThe result of mitosis is two diploid sister cells, since their genetic content is identical.

Meiosis

This type of cell division occurs only in the formation of gametes.In the case of humans, these are the spermatozoa and ova, cells that are responsible for shaping fertilization (they are the so-called germ cell line). Simply put, meiosis is like two consecutive mitoses.

During the first meiosis (meiosis 1) a process similar to that explained in mitosis occurs, except that the homologous chromosomes (the pair) can exchange fragments with each other by recombination. This does not occur in mitosis, since in mitosis they never come into direct contact with each other, unlike in meiosis. It is a mechanism that offers more variability to genetic inheritance. In addition, it is the chromosomes that separate, what separates are the homologous chromosomes, and not the copies..

Another difference between mitosis and meiosis occurs with the second part (meiosis 2). After two diploid cells have formed, they immediately divide again. Now the copies of each chromosome are separated, so that the final result of meiosis are four haploid cells, since they have only one chromosome of each (not pairs), to allow fertilization to form new pairings between the chromosomes of the parents and enrich genetic variability.

General summary

To summarize the differences between mitosis and meiosis in humans, we will say that the end result of mitosis are two identical cells with 46 chromosomes (pairs of 23), while in the case of meiosis are four cells with 23 chromosomes each (unpaired), plus their genetic content can vary by recombination between homologous chromosomes.