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Meiosis

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The meiosis is considered one of the most important biological discoveries in history, since it is one of the processes of cell division essential for living beings governed under the chain of sexual reproduction.

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What is meiosis?

Meiosis is one of the processes of cell division most mentioned in what are the basic studies, together with the recognized mitosis, this explains what is recognized as the multiplication of cells , as from a single cell another is obtained, however , the one obtained from a cell does not have the same genetic load, but is given half the chromosomes as the cell from which, so to speak, it was born. This happens since not only one cell reproduces, when others divide they also create another cell with half of its chromosomes, they are generally called gametes , the first duty of these gametes to be able toto develop and become complete cells is to look for another gamete, so that in the process of fertilization they intertwine and being united to be a cell with the correct number of chromosomes. This process of cell division only occurs in biochemical organisms that have the ability to reproduce sexually, this process also tends to be called gametogenesis , that is, it produces the sex cells that will later act and work towards fertilization .

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  • History
  • Characteristics of meiosis
  • Process
  • Meiosis 1
  • Meiosis 2
  • In which cells does meiosis occur
  • How it differs from mitosis
  • Importance

History

This biochemical process of cell division was discovered and described for the first time thanks to a renowned German biologist like Oscar Hertwig, in 1876 , he became aware of this process thanks to an exhaustive analysis and study that he made of sea urchins.

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Although it was mentioned for the first time on that date, it was not fully taken into account, it was not until 1883 that it was described again at the chromosomal level, based on an analysis study of the parasitic worms called Ascaris, this study was carried out by the Belgian zoologist Edouard Van Beneden, at the time only budding was recognized as a reproduction process , which consists of asexual reproduction, it was therefore a great find to realize that in this type of reproduction,a single cell divided and that the gamete produced consisted of only half of its chromosomes and then by synapse or innate biochemical process to search for another gamete and join, in order to regain the right amount of chromosomes, was simply wonderful.

However, despite the fact that the second description of meiosis caused controversy and admiration, it was not until 1890 that its importance in sexual reproduction was highlighted thanks to the biologist August Weisman, who discovered the finding that it was necessary the division of a diploid cell for the generation of four haploid cells so that these later maintain a standardized number of chromosomes.

Characteristics of meiosis

Meiosis has unique and singular characteristics , like any other cellular process, one of its most common characteristics is that the division of the primary cell, that is, the diploid, is necessary to procreate, when the haploid cells are separated and with half of its chromosomes can be united in the fertilization process, in which they not only complete the organic process , but also make up the genetic components of the fetus.

Process

This division process is divided into three phases, which are the following:

  • G1 phase: The main or progenitor cell increases excessively in size, since it begins to manufacture on its own what are organelles, proteins, and various cellular materials.
  • Phase S: In this phase the genetic material is replicated, the genetic loads are doubled, thus initiating two new chains of cells joined by a centromere, the chromosomes go from having one chromatid to having two, thus doubling 98% of the DNA.
  • G2 phase: The cell continues to increase its amount of mass, in order to achieve its complete division.

Meiosis 1

What does it consist of?

This is the first phase of Meiosis, in which the cells are reduced , that is, in this phase is in which the diploid cell divides and what is genetic diversity is generated.

Phases

Prophase I: It is the most complex stage of the process, it is divided into the following stages:

  • Leptotene.
  • Zygotene or zygonema.
  • Paquiteno.
  • Diplotene.
  • Diakinesis

Metaphase I: What is called the achromatic spindle develops in its entirety, thus placing the chromosomes in the equatorial plane and joining their centromeres to what is the spindle.

Anaphase I: Male and female chromosomes are located at different poles, so each meiosis changes depending on the organism and is totally random.

Telophase I: This is when one of the first processes is completed and the chromosomes are divided, the daughter cells have half of the chromosomes of their parents.

If this procedure is not followed, it would not be possible to proceed to what is Meiosis II, therefore, this division of cells would not exist.

Meiosis 2

What does it consist of?

This stage of meiosis is similar to mitosis , the chromatids of each chromosome, which were previously identical are no longer identical due to the combination of cells, here the chromatids separate to give way to daughter cells each with a charge distinct chromosome.

Phases

Prophase II:

  • Early prophase II: The envelope of cells and chromosomes begins to disappear, thus showing long filamentous chromantine bodies.
  • Late Prophase II: Chromosomes progressively shorten and thicken.
  • Metaphase II: The spindle fibers bind directly to the centromeres of each chromosome.
  • Anaphase II: The chromatids separate from their centromeres and the chromosomes move to opposite poles.
  • Telophase II: A member of each pair of homologous cells is found in a different pole, each of these is an unduplicated chromosome and what is known as cytokinesis occurs.

In which cells does meiosis occur

Meiosis makes its way into diploid cells , since they are capable of dividing and creating daughters, that is, cells starting from themselves which are called haploid cells.

How it differs from mitosis

The most relevant difference between mitosis and meiosis is that the first of these two occurs only in asexual reproductive organs.

Importance

Meiosis is extremely important , both for the optimal functioning of the organism , and for what is sexual reproduction, thanks to this the male and female genetic loads become fertilized in the ovules, that is, without this process it would be relatively impossible to fertilize Correct way, added to that, the fetus would not have any genetic load from its parents.

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