If you look at the faces of your family members, you will definitely find one or two similarities. It can be from the shape of the face, skin color, eye shape, eyebrow curve, ear shape, even body height. For example, you have round eyes like your mother, while your brother or sister’s eyes are almond-shaped, similar to your father’s.
Then, another example, your height is above average like your father while your brother tends to be shorter, similar to your mother. Differences like this are commonplace in a family. The question is, why are there differences between you and your siblings even though you come from the same parents?
To answer this question, you need to understand what meiosis division is which is related to the formation of gamete cells in the body. So, instead of having to worry about looking for material on meiosis division from various sources, let’s look at the complete information in this article.
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What is Meiosis Division
You need to know, every cell on this earth, including cells in the human body, will always divide. In the process, there are two types of cell division, namely mitosis and meiosis. So, what is meant by meiotic division is the division carried out for reproductive function. The process occurs in the gonad cells in the sexual organs of living creatures that reproduce.
In general, meiotic division occurs in two stages which will later divide the cell twice. Thus there will be four cells, each containing the parent’s chromosomes.
Meiosis is a type of cell division that produces four daughter cells, each of which has half the number of chromosomes of the parent cell.
It cannot be denied that meiosis and mitosis are quite foreign topics to our ears. For this reason, you need to read the book Cell and Molecular Biology for Health Professionals because it discusses the molecular basis of biological activity within and between cells, including synthesis, modification, molecular mechanisms and interactions.
Purpose of Meiosis Division
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The result of meiotic division is the creation of gamete cells or reproductive cells such as egg cells or sperm in humans. So you could say that the purpose of meiotic cell division is to produce these gamete cells. So, why must sex cells be formed by meiotic division? To answer this question, you must first know the key, namely that every living creature has a fixed number of chromosomes.
Meiotic division is important for the process of sexual reproduction.
From generation to generation, the number of chromosomes in living things never changes. For example, humans have long had 46 chromosomes or 23 pairs of chromosomes, mice have 40 chromosomes or 20 pairs, while dolphins have 44 chromosomes or 22 pairs.
A human child is the result of the fusion of sperm cells from the father and egg cells from the mother. According to simple logic, a human child should have 92 chromosomes because he gets 46 chromosomes from his father and 46 chromosomes from his mother. But, the facts are not like that. A human child still has 46 chromosomes even if he has two parents with 46 chromosomes. This is where the function of meiotic division is needed.
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With this division, the father’s and mother’s chromosomes will be divided so that children born from the fusion of sperm cells and egg cells have the same number of chromosomes as humans in general, namely 46 chromosomes.
So, in conclusion, meiosis plays an important role in the survival of every living creature that reproduces. Through this division, the number of chromosomes will not change from one generation to the next. On the other hand, meiosis division also causes you to have similarities with your parents and siblings but still have differences.
Meiosis Division Stages
Meiosis cell division occurs twice, namely meiosis I and meiosis II. Well, in each phase there are 4 different stages, namely prophase, metaphase, anaphase and telophase.
Meiotic division allows genetic recombination to occur, namely the transfer of genetic material from one chromosome to another.
Meiosis I
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Prophase I
You need to know that in this prophase there are five subphases consisting of leptotene, zygotene, pachytene, diplotene, and also diakinesis.
In Leptote
Leptotene is the stage when leptotene chromatin becomes denser (condensation) and turns into chromosomes.
Zigoten
Zygotene is a process that occurs after the leptotene process is complete. In this phase, the chromosomes will form synapses which then pair with their homologues.
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Pachytene is the phase when the chromosome arms double. After that, these double chromosomes will form a chiasma or crossing over area for the homologous chromosome pair.
Diplotene
In the diplotene stage, chromosome recombination occurs due to the process of chromatids crossing over at the chiasma.
Diakinesis
In this final phase, the centrosome will split into two centrioles and the nuclear membrane will become blocked. Centrioles themselves are components in cells whose job is to attract chromosomes.
Later, the two centrioles produced from this division will move towards each pole. When the diakinesis phase has ended, the prophase stage of meiosis 1 division can be said to be complete.
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So in short, prophase 1 begins with chromatin condensation. However, different from the prophase phase found in mitosis, in meiotic prophase the attachment of two homologous chromosomes occurs.
These attachments will then form a tetrad. Then crossing over will occur in the chiasmata which is the meeting place between the two chromosomes. This crossing over process results in differences in genetic characteristics from the parent cells.
This process is carried out so that the new cells produced have the best quality chromosomes. Examples include short and pug or tall and sharp. After that, characteristics appear such as the centromere moving towards the poles, spindles appearing, the nuclear membrane and nucleus disappearing, and the homologous chromosomes separating slightly.
Metaphase I
Metaphase 1 is the phase when the chromosomes are aligned at the cell equator and all the spindles are attached to the chromosome kinetochores. However, in metaphase 1, the chromosomes still have a tetrad shape.
Anaphase I
In anaphase 1, the chromosomes that are approaching the poles only have 2 DNA. This happens because all the chromosomes have moved. This is different from anaphase in mitosis where each pole gets 4 DNA because only the chromatids move.
Telofase I
In telophase 1 cell division occurs so that each cell which initially had 4 DNA becomes only 2 DNA. In the process, parts of the cell nucleus are formed again with a different chromosome arrangement.
Meiosis II
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Prophase II
After telophase 1 is complete, the process continues to the second division stage. The process itself begins with the spindle appearing and the chromosomes starting to move closer to the equator.
Meiotic division also occurs in the process of forming gametes, namely egg cells and sperm cells.
Metaphase II
In metaphase II, the two chromosomes are aligned at the equator and the spindle fibers are attached to the kinetochore.
Anaphase II
In anaphase II, sister chromatids that have the same genetic characteristics will also move towards the centromere via the spindle thread pathway. In this division, the same number of equational divisions occurs.
So, in contrast to Anaphase I, where the number of chromosomes is reduced by half, in Anaphase II, the number of chromosomes remains, namely 2 DNA or haploid.
Telophase II
After the division process at this last stage, the situation will be like this:
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- The two new cells produced are haploid in nature
- The four cells are genetically different because of the crossing over process.
- The cell membrane and nucleus will form again
- Then the chromosomes will turn back into chromatin
- Finally, the cytoplasm will separate.
From the explanation above, it can be summarized that meiosis I phase is the process when homologous chromosomes separate, while meiosis II is the process when sister chromatids separate.
Then, in meiosis I, there is a process of reducing chromosomes and also crossing over traits which then produces two daughter cells. Meanwhile, in meiosis II, there is no process of reducing chromosomes and crossing over traits, resulting in four daughter cells.
Characteristics of Meiosis Division
The characteristics of the first meiotic division are that this division takes place in the gonad cells in the sexual organs to produce gamete cells. Second, meiosis division has two stages, namely meiosis I and meiosis II.
The third characteristic, meiotic division will produce four haploid daughter cells. These daughter cells will not divide again. Then the last characteristic, meiotic division only occurs in adult organisms.
Example of Meiosis Division
If you already understand the meaning, stages and purpose of meiotic division, it will be easier for you to imagine an example of this division. Because meiosis division in the reproduction process occurs in animals, plants and also humans. This means that meiosis division takes place in the cells of living things, for example egg cells and sperm cells in animals and humans or ovule cells and pollen cells in plants.
Differences between Meiosis and Mitosis
The main difference between meiosis and mitosis basically lies in several aspects, such as the purpose of the process, the number of cell divisions, where the division occurs, and also the characteristics of the daughter cells. Mitosis can occur in all body cells that are multiplying. In addition, in this division there is only one division stage in one cell division cycle.
Then, there are no pairs of homologous chromosomes because what separates is the chromatids that move towards different poles. Then there is no exchange of chromosome segments and occurs in romantic cells. Mitosis consists of the stages “prophase-metaphase-anaphase and telophase which are alternated by interphase. Mitosis is carried out during a person’s growth period. The resulting daughter cells are diploid.
Daughter cells (new cells) made from mitotic division have the same genetic structure as the parent cells. Mitotic division takes place in a short time. Then, the number of chromosomes in each nucleus is still maintained in daughter cells. Finally, the end result is two new identical cells.
Meanwhile, meiosis division only occurs in gonad cells which takes place during the formation of gamete cells. Apart from that, meiosis division has two stages, namely meiosis I and meiosis II.
Meiosis I is a division stage that produces two daughter cells, each of which has half the number of chromosomes of the parent cell.
In meiosis I, there are pairs of homologous chromosomes where each member of the chromosome pair will then migrate to different poles. Meanwhile, in meiosis II, chromatid separation occurs as in mitosis.
Meiosis II is a division stage that produces four daughter cells, each of which has half the number of chromosomes of the parent cell.
Then, in meiosis, crossing over occurs between paired homologous chromosomes. Meiotic division has the stages “prophase I – metaphase I – anaphase I – telophase I – prophase II – metaphase II – anaphase II – telophase II, without interphase”. Meiosis division is carried out to maintain the number of chromosomes.
The daughter cells resulting from meiotic division are haploid and have half the number of chromosomes as the parent cells. The cell division process takes place quickly. The number of chromosomes in meiotic cell division is half that of the original nucleus. Then the final result of meiotic division is four new cells with half the number of chromosomes as the parent cell.
To make it easier for you to understand the difference between meiosis and mitosis, try looking at the table below.
| Difference | Meiosis | Mitosis |
| Number of divisions | Generally two divisions and more gradual | There is only one division |
| Objective | To reduce the number of chromosomes and also requires recombination and sexual reproduction | For the reproduction of unicellular eukaryotic organisms and also for asexual reproduction, growth and cell repair. |
| Duplicate content | In the first division, there is no duplication of chromosomes and cytoplasm. Meanwhile, the second division is the same as mitosis and the number of chromosomes does not decrease. | The content is in the form of chromosomes and cytoplasmic material. |
| Cross | A crossover process occurs | No crossover process occurs |
| Centromere | The centromeres do not separate in the anaphase I phase, but in the anaphase II phase the centromeres become separated. | The centromeres separate during anaphase |
| Cytokinesis | Cytokinesis occurs twice, namely in telophase I and telophase II. | Cytokinesis only occurs once |
| Number of daughter cells | four cells | two cells |
| Characteristics of daughter cells | Not identical to stem cells because in the process a combination of genes occurs | Identical to stem cells |
| Characteristics of the chromosomes of daughter cells resulting from diploid parent cell division | Haploid | Diploid |
| Role for multicellular eukaryotic organisms | Produces gamete cells | Produces somatic cells |
| Interkinesis | There is interkinesis between meiosis I and meiosis II | No interkinesis |
| Metaphase | Metaphase II: chromosomes line up on the equator in 1 row | The chromosomes are lined up in one row at the equator |
| Sister chromatids (chromosome duplication) | Occurs in the middle of prophase I or pachytene phase. | Occurs at the beginning of prophase |
| Synapsis of homologous chromosomes | Occurs in prophase I | Not occur |
| Crossing over of genes on chromosomes | There is crossing over | There is no crossing over |
| Centromere during anaphase | In anaphase I, the centromeres have not separated while in anaphase II the centromeres have separated. | The centromere divides in 2 so that the chromatids separate during anaphase. |
| Anaphase | Anaphase I separates pairs of homologous chromosomes while anaphase II separates sister chromatids | Separating sister chromatids. |
If you look at all the differences between meiosis and mitosis above, actually meiosis is more towards reproduction while mitosis is more towards growth.
However, it turns out that there are living creatures that do not require meiosis to reproduce, for example amoebas. Amoebas reproduce through the process of amitosis or binary fission which is carried out by dividing directly without having to go through the stages of meiosis.
Closing
The main purpose of cell division is to form new cells. From these new cells, tissue will form, then tissue will form organs, then people will become organisms.
That is why, meiosis division can be carried out by all organisms, starting from plants, animals, and also humans. Note that the organism must have a structure of cells.
Apart from that, new cells will also replace old cells that have died or reached their age limit. Because each cell has its own lifespan, it is necessary to regenerate through cell division so that each organism will survive.
If an organism has less cells than it should, the organism will face various problems. For example, a certain disease appears which then affects all the organ system tissues in the body.
On the other hand, if an organism has a greater number of cells than it should, it will give rise to tumor cells due to excessive growth of new cells. If you feel that the discussion about meiotic division in this article is not enough, you can buy the book, Practice Questions and Discussion on Selections for the National Science Olympiad in Biology, Sixth Edition . In this book there are examples of questions that will make it easier for you to understand meiotic division.