5 Characteristics of mitosis

No cell appears by spontaneous generation, that is, a complex reproduction process is always carried out so that it can multiply and renew itself. Within this process it is determined that a cell can only arise from the division of another. That’s their way of reproducing.

Cells alone do not live long. If it were not for its reproduction, no living being would live so many years. The renewal and generation of cells happens in every part of the body and this is how we can maintain life.

Thus, although it may go unnoticed, within each body the cells are always in movement and in action. In this sense, mitosis is a process only for eukaryotic cells. In this article we will talk about the 4 phases of mitosis in an animal cell.

What is mitosis

Mitosis is a type of cell division in which a mother cell divides and results in two new cells , called daughter cells, which are genetically identical. In other words, the mother cell copies and transmits its genetic information to the new cell formed, so both have the same number of chromosomes. For example, if the mother is diploid, that is, she has two sets of homologous chromosomes in her nucleus, the pair will be diploid.

Specifically, mitosis is carried out by all the cells in our body , except the sexual ones. It is not an isolated process, but is part of the cell cycle in which other stages are involved, that is, the cell does not keep dividing all the time, so it is not always in mitosis. In fact, mitosis occupies a small part of the life of a cell, approximately 10%.

When the cell is not in mitosis, it is said to be in interphase. Before dividing, a cell that is at the end of interphase must prepare itself by duplicating its DNA, which leads to the appearance of centrioles, organelles with a cylindrical structure with a function that we will explain later.

Characteristics

Mitosis is the process by which a cell divides into two identical daughter cells. It is an essential process for growth, repair, and maintenance of tissues in multicellular organisms.

Here are the key characteristics of mitosis:

  1. Cell Division: Mitosis involves the division of a single parent cell into two identical daughter cells. This ensures that each daughter cell receives a complete set of genetic material and cellular components.
  2. Interphase: Before mitosis begins, the cell goes through a phase called interphase, during which it grows, carries out its normal functions, and replicates its DNA. Interphase consists of three subphases: G1 (growth), S (DNA synthesis), and G2 (preparation for mitosis).
  3. Phases of Mitosis: Mitosis is divided into four phases: prophase, metaphase, anaphase, and telophase. During prophase, the DNA condenses into visible chromosomes, and the nuclear membrane begins to break down. In metaphase, the chromosomes line up at the center of the cell. During anaphase, the sister chromatids separate and move towards opposite ends of the cell. In telophase, the nuclear membrane reforms, and the chromosomes begin to decondense.
  4. Spindle Apparatus: Mitosis involves the formation of a spindle apparatus, which consists of microtubules and other proteins. The spindle apparatus helps in the separation of sister chromatids during anaphase. It attaches to the chromosomes at specialized structures called kinetochores.
  5. Cytokinesis: After the completion of mitosis, cytokinesis follows, which is the division of the cytoplasm. In animal cells, a contractile ring forms and constricts, leading to the formation of a cleavage furrow, resulting in the separation of the two daughter cells. In plant cells, a cell plate forms between the daughter cells, eventually developing into a new cell wall.

Overall, mitosis is a highly regulated and precise process that ensures the faithful distribution of genetic material and cellular components to daughter cells. It plays a vital role in the growth and development of organisms and the maintenance of tissues.

The 4 phases of Mitosis

Prophase

Prophase is the first phase of mitosis. In it, the nuclear membrane remains intact and we can observe a nucleolus. In addition to DNA duplication , centrosome duplication also takes place as follows:

  • The centrosome is located in the cytoplasm very close to the nucleus and, in the case of the animal cell, contains two centrioles .
  • A structure made of microtubules, called the mitotic spindle, begins to form between the centrosomes.
  • In the nucleus, chromatin condenses and organizes into chromosomes. This is when the nucleolus disappears from view.
  • In late prophase, shortly before metaphase, chromosomes are visible, but in most multicellular organisms, the cell loses its nuclear membrane and we can no longer recognize the nucleus.

The accommodation of centrosomes can occur in the following way:

  • Open mitosis : the centrosomes are housed at the poles of the cell, that is, if they are located near what was the nucleus, they separate away towards the ends and there they attach to the microtubules. Open mitosis is most common in plants and animals.
  • Closed mitosis : when the nucleus does not disappear and the chromosomes remain within it. Closed mitosis occurs more in fungal cells.

Metaphase

In metaphase, the chromosomes are aligned in an area called the metaphase plate or equatorial plate, as it is similar to the imaginary line on Earth known as the equator.

Certain regulatory proteins verify if there are no lagging chromosomes or if there is any element not hooked or anchored to the microtubules. This revision is called a spindle checkpoint . If a chromosome is not properly anchored, the process of mitosis stops until the microtubules direct it to the correct position.

Not everything is a connection between microtubules and chromosomes. There is also the union between microtubules of the opposite pole, which provides stability to the entire structure.

Anaphase

In anaphase, the proteins that join the chromatids of the chromosomes , filaments that make up the chromosomes, separate and move away to opposite poles of the cell . For their part, the microtubules that anchor the chromatids degrade.

The attachments between microtubules that occurred in metaphase push the cell toward different poles, elongating the cell.

Telophase

In telophase all the microtubules have been degraded and the nuclear membrane is formed around the chromatids that were separated at each pole, that is, two nuclear membranes are formed located at the ends.

Within each nuclear membrane a nucleolus appears, the structure of the chromosomes disperses and the contained DNA acquires the filamentous appearance that it had in the interphase. Here the process of mitosis concludes.

Cytokinesis

Cytokinesis itself is not part of mitosis , but is a complement to the end of anaphase or during telophase, depending on the cell type. In animal cells, when there are already two nuclear membranes and two nucleoli, a thinning occurs in the equatorial area . As if we were squeezing a bar of plasticine right in the middle, breaking it into two pieces. In this cellular process, that division ‘thread’ is actually a band of actin filaments, a type of protein.

In plant cells, cytokinesis occurs due to the synthesis of a rigid wall that divides the daughter cells.

In short, mitosis in animal cells is not the same as that of plant cells, although some processes are similar. For example, the plant cell does not contain centrioles, but microtubules organize in the cytosol to form the mitotic spindle.

What is the benefit of mitosis?

Without a doubt, mitosis is an interesting and wonderful process that living organisms have. Think about the times you have injured your skin when you were little. Imagine now that the blood you lost cannot be recovered or that your skin is marked or injured forever. The same thing happens in wildlife. The wounds suffered by animals or the growth of a plant require mitosis.

In this sense, what mitosis does is help replace cells that have been lost or damaged. The skin regenerates thanks to the development of new cells and these repair the affected area. It is worth mentioning that cells only divide when a chemical signal tells them to do so. This signal is interpreted by the nucleus, begins to take action and leads to what we know as mitosis.

The problem can arise when certain cells begin to divide even without receiving any signal. This group of rebellious cells is called cancer cells and is responsible for serious deterioration in health.

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