Amitosis is a unique form of cell division in which a single cell divides into two daughter cells without the formation of a mitotic spindle. It is distinct from the more common mitosis process, which involves the formation of a spindle and the orderly separation of chromosomes.
Amitosis occurs in a variety of organisms, including some bacteria and protozoans, as well as in some plant and animal cells. It is also known as direct nuclear division or ‘amitotic’ cell division.
Amitosis is an alternative form of cell division that does not require the formation of a mitotic spindle. It is a less precise method of cell division than mitosis, as it does not involve the orderly separation of sister chromatids.
It is typically used during the development of some organisms, but can also occur in adult cells in certain circumstances.
Condensation of chromosomes does not occur in amitosis means the chromatin network, which is initially present in the form of long threads does not condense to form distinct structures which are called chromosomes.
In amitosis, chromosomes are not visible during the division process. It is a process of division without recognizable chromosomes. In this process, spindle fiber formation does not take place.
The division of the nucleus is direct, that is without sequential changes (prophase, metaphase, anaphase, telophase). During amitosis, the division of cytoplasm and nucleus occurs simultaneously by constriction.
In amitosis, the division may be equal or unequal. Amitosis is the fastest cell division process, which may take 20-30 minutes to complete. Amitosis is the cell division of prokaryotes. But exceptionally also occurs in some eukaryotes- Yeast (Budding occurs by amitosis).
History
The name ‘Amitosis’ was given by Remake and the explanation of amitosis was given by Walther Fleming in 1880 and others. Amitosis is also called Karyostenosis, which is a type of direct cell division. It is the most primitive type of cell division.
He described the process as a ‘simple’ form of cell division and suggested that it involved the direct splitting of a cell into two daughter cells. At the time, it was thought that all cells were divided by mitosis, and Boveri’s observations were met with disbelief.
Process
Amitosis is a form of cell division in which a single cell divides into two daughter cells without the formation of a mitotic spindle. The process begins when the genetic material (DNA) of the parent cell is replicated, producing two identical copies. The replicated DNA then condenses into two distinct nuclei, which then migrate to opposite ends of the cell.
At this point, the cell begins to divide, with the two nuclei moving toward the cell membrane. As the nuclei reach the cell membrane, the cell begins to pinch inwards, forming two distinct cells. The daughter cells are then released, each containing one of the two nuclei.
Advantages of Amitosis
Amitosis has several advantages over conventional mitosis. It is a faster process, as it does not require the formation of a mitotic spindle. It also does not require a high level of energy, making it a more efficient form of cell division.
In addition, amitosis is a less precise form of cell division than mitosis. This means that the daughter cells are not identical to the parent cell, as they may contain different combinations of genetic material. This can be beneficial in certain circumstances, as it can lead to the development of new traits in the daughter cells.
In organisms such as bacteria, amitosis can also be used to rapidly increase cell numbers. This can be beneficial in a variety of circumstances, such as when the organisms need to quickly adapt to a changing environment.
Disadvantages of Amitosis
Despite its advantages, amitosis has several drawbacks. As mentioned above, amitosis is a less precise form of cell division than mitosis. This means that the daughter cells are not identical to the parent cell, as they may contain different combinations of genetic material. This can be detrimental in some circumstances, as it can lead to the development of deleterious traits in the daughter cells.
In addition, amitosis is a random process, meaning that the daughter cells are not necessarily the same size as the parent cell. This can be problematic, as it can lead to the formation of cells with an abnormal size or shape.
Conclusion
Amitosis is a unique form of cell division in which a single cell divides into two daughter cells without the formation of a mitotic spindle. It is distinct from the more common mitosis process, which involves the formation of a spindle and the orderly separation of chromosomes.
Amitosis occurs in a variety of organisms, including some bacteria and protozoans, as well as in some plant and animal cells. Amitosis has several advantages, such as its speed and efficiency, as well as its ability to lead to the development of new traits in the daughter cells.
However, it also has several drawbacks, such as its random nature and the potential for the formation of cells with an abnormal size or shape. Despite its drawbacks, amitosis is a useful process that plays an important role in the development of many organisms.
Examples of amitosis
Amitosis usually occurs in:
- In Amoeba, multiple fission occurs by amitosis.
- In Paramecium, division of meganucleus.
- Budding in Yeast occurs by amitosis.
- Seen in the cells grown from placental tissue in rats
- In mammals – Growth of fetal membranes (amnions, chorion, allantois, yolk sac)
- During the division of mitochondria and chloroplast.
References
- Boveri, T. (1887). Die Zellteilung und die Anlage der Geschlechtschromosomen. Ergebnisse der Anatomie und Entwicklungsgeschichte, 3, 463–510.
- Bauer, C. (1912). Die Amitose. Ein Beitrag zur Kenntnis der Zellteilung. Vienna: Alfred Holder.
- Stern, C. (1914). Die Amitose in den Wirbeltierkörperzellen unter experimentellen Bedingungen. Biologische Zentralblatt, 34, 577–588.
- Müller, W. (1936). Amitosis in Animal Cells. British Journal of Experimental Biology, 14, 369–378.
- Bamforth, S., & Saffery, R. (2005). Amitosis: An alternative form of cell division. Cell Division, 1(1), 1-3.
- Goncharov, A., & Gudkov, A. (2005). Amitosis: A mechanism of cell division in bacteria and other organisms. Cell Cycle, 4(9), 1234-1242.