The cells in our body continually divide by mitosis, a process essential for tissue growth and regeneration. This mechanism allows a mother cell to divide into two daughter cells, genetically identical to each other and to the original cell. In this division, the DNA in the cell nucleus is distributed into two identical groups of chromosomes.
In this article, we will explain in detail everything you need to know about mitosis, its phases and its importance in multicellular organisms.
What is mitosis
Mitosis is a type of cell division. in which a parent cell divides to form two genetically identical daughter cells. During this process, the duplicated genetic material of the original cell is organized and distributed into chromosomes so that each daughter cell receives a complete and exact copy of the genetic information.
In multicellular organisms such as humans, mitosis not only enables growth, but is also key to repairing damaged tissues. It is also the process by which eukaryotic unicellular organisms (such as yeast) reproduce.
The main objective of mitosis is ensure proper DNA distribution, since any error in this process can cause the formation of cells with genetic abnormalities, which could lead to diseases such as cancer.
During mitotic divisions, DNA is not distributed randomly. It is organized and distributed into the duplicated chromosomes in a series of well-defined phases.
Phases of the cell cycle and mitosis
To understand mitosis, we must first know the cell cycle, which consists of two main phases: interphase and the mitotic phase.
the interface
Interphase is the longest phase of the cell cycle and has several subphases:
- G1 phase: The cell grows and performs its normal functions. It is a period of intense metabolic activity and cell growth.
- Phase S:In this phase, the cell duplicates its DNA, preparing for division.
- G2 phase: It is a second period of growth, during which the cell prepares to begin mitosis.
Mitotic phase
The mitotic phase, also known as mitosis, is divided into five main stages, which allow the formation of two identical daughter cells:
1. Prophase: During this phase, the chromosomes condense, that is, they become compacted and visible under a microscope. The nuclear envelope begins to break down and the mitotic spindle, a structure made of microtubules, forms between the poles of the cell. This structure will be essential for moving the chromosomes during the following stages of mitosis.
2. Prometaphase: At this stage, the nuclear envelope completely disintegrates and the mitotic spindle begins to interact with the chromosomes. These chromosomes, now fully condensed, attach to the microtubules through special structures called kinetochores.
3. Metaphase: Chromosomes line up in the center of the cell, forming the metaphase plateThis alignment is crucial, as it ensures that each daughter cell receives an exact copy of the genetic material.
4. Anaphase: Sister chromatids (each of the two parts of a replicated chromosome) separate and are pulled towards the poles of the cell by microtubules. In this phase, it is ensured that each daughter cell receives a complete set of chromosomes.
5. Telophase:In this final phase, the chromosomes reach the poles of the cell and the nuclear membranes around each set of chromosomes are reconstituted. The chromosomes begin to decondense and the microtubules of the mitotic spindle disappear.
Cytokinesis: the final division
Once telophase has ended, cytokinesis occurs, which consists of the division of the cell cytoplasmIn animal cells, a furrow forms that pinches the parent cell, separating it into two daughter cells. In plant cells, cytokinesis occurs by the formation of a new cell wall between the two daughter cells.
Importance of mitosis in living beings
Mitosis is essential for the development and maintenance of multicellular organisms. Some of its most important functions are:
- tissue repair: In case of injuries, mitosis allows the regeneration of damaged cells.
- Growth: It is responsible for the increase in size of multicellular organisms, such as humans, from a single initial cell to trillions of cells.
- Reproduction in unicellular organisms: In some unicellular eukaryotes, mitosis is the main mechanism of asexual reproduction.
Mitosis is also closely related to the genetic stability of organisms, as it ensures that daughter cells receive an exact copy of the parent cell's genetic material.
Errors in mitosis: the consequences
When mitosis does not occur correctly, errors in the distribution of chromosomes can occur. These errors, known as aneuploidies, can give rise to cells with an abnormal number of chromosomes.
Aneuploidies can have serious consequences for the health of an organism. For example, when cells contain too many or too few chromosomes, genetic diseases or cancer can develop. One of the best-known aneuploidies in humans is Down syndrome, which occurs when there is an extra copy of chromosome 21.
In addition to errors in the number of chromosomes, errors can also occur mutations during DNA replication in the S phase of the cell cycle. These mutations can disrupt normal gene functions, which can also trigger the development of diseases.
To minimize these risks, cells have error control and correction mechanisms that are activated when they detect problems during mitosis. However, these mechanisms are not infallible and, in some cases, errors can go unnoticed.
Thus, mitosis, although a finely balanced process, can lead to serious problems if it does not develop properly.
Mitosis is an essential process for life. It is what enables organisms to grow, regenerate and maintain genetic stability. However, when this process fails, the consequences can be serious, so it is vital for cellular health that mitosis functions properly.