Mitosis Metaphase: Process, Significance & Applications

Mitosis is a cell division process that keeps us alive and healthy. Whenever we face an injury, our body needs to replace damaged cells with healthy new ones to repair them, mitosis plays a critical role in this process. Metaphase is the mitotic phase that comes after prophase and prometaphase but before anaphase. In this stage, the duplicated genetic material is transferred from the parent cell’s nucleus to the 2 identical daughter cells. In this article, we will learn about the mitosis metaphase, its significance, applications, and related sample questions.

Keyterms: Cell divison, Cell, Mitosis, Metaphase, Mitotic phase, Zygote, Nucleus, Prophase, Prometaphase, Anaphase

Read More: Chromosomal Theory of Inheritance

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Mitosis

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Mitosis is the process by which a single zygote becomes a complete creature in multicellular eukaryotes. It is the stage of the cell cycle when freshly duplicated DNA is segregated from two new cells. This is an important mechanism in single-celled eukaryotes since it is asexual reproduction. Mitosis is divided into numerous stages, or phases, which will be explored further. Growth and DNA replication are two other stages in the cell cycle that are essential for mitosis to occur.

Mitosis is the process in which the vast majority of cell divisions take place in our bodies. During development, growth, and throughout an organism's existence, mitosis replaces old, worn-out cells with new ones, populating the body with cells. Mitotic divisions are a type of reproduction used by single-celled eukaryotes such as yeast, resulting in the addition of a new individual to the population.

In all of these circumstances, mitosis occurs with the purpose to ensure that each of the daughter cells has a complete set of chromosomes. Cells with too few or too many chromosomes normally do not function effectively, and as a result, they may not survive or potentially cause cancer. As a result, when cell mitosis occurs, they don't divide their DNA at random and fling it into two piles for the two daughter cells. They broke apart their replicated chromosomes in a meticulously planned set of steps.

Read More: Mitosis and Meiosis

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Significance of Mitosis

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• It is an equational division in which identical daughter cells with the same number and same genetic makeup as the parent cell are created.
• It is responsible for the genesis and development of multicellular creatures from a single-celled zygote.
• All of the cells formed by this division have the same number of chromosomes. As a result, the daughter cells inherit the parent cell's characteristics.
• It aids in the correct size maintenance of the cells.
• Mitosis aids in the repair of worn-out bodily tissues, the replacement of damaged or missing components, wound healing, and the regeneration of detached parts (as in the tail of lizards).
• In unicellular organisms, it is a technique of multiplication.
• If mitosis goes unchecked, it can lead to unregulated cell proliferation, which can lead to cancer or tumors.

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Metaphase

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Metaphase is a third stage in the cell division process (mitosis or meiosis). Individual chromosomes are rarely visible in the nucleus of a cell. The chromosomes condense and become distinct during the metaphase stage of mitosis as they align in the middle of the dividing cell. During the karyotyping method, which is used to look for chromosomal abnormalities, metaphase chromosomes are employed.

Metaphase involves the process of separating duplicated genetic material carried in a parent cell's nucleus into two identical daughter cells. The metaphase checkpoint, which indicates that the cell is ready to divide, is a crucial checkpoint in mitosis during which the cell's survival is ensured.

During prometaphase, all of the long protein filament microtubules, also known as kinetochore microtubules, bind to the sister chromatids' centromeres, and hence the metaphase stage commences.

The microtubules begin to exert a strong tug on the chromosomes. As a result, the chromosome travels to the cell's center. The metaphase plate is the name for this area. As a result, each cell is given a complete genome.

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Process of Metaphase

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Metaphase is referred to the process wherein the duplicated genetic material that is in the parent cells’ nuclei splits into 2 daughter cells that are identical in nature. 

• The chromosomes are aligned at the center of the cell during metaphase by pulling and pushing, a process known as a cellular tug of war. 
• When replicated chromosomes are joined at the centromere, sister chromatids develop.
• The prophase stage creates radial microtubules known as kinetochores surrounding the centrosome before metaphase.
• Kinetochore microtubules are long protein filament microtubules that connect the kinetochores to the cell poles on each end. 
• The sister chromatids are pulled back and forth by the kinetochore tubules until they are aligned at the cell's equator.
• A metaphase checkpoint also occurs during metaphase.
• By evaluating chromosome alignment and kinetochores attachment, the metaphase checkpoint, also known as the spindle assembly checkpoint, ensures that the cell is ready to split.
• Despite the differences in chromosomal alignment between mitosis and meiosis, both types of cell cycles require the spindle assembly checkpoint to occur during metaphase.
• When these procedures are performed successfully, the cell enters the fourth phase of mitosis, known as anaphase.

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Metaphase of Mitosis

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• After the chromosomes have contracted during prophase, the cell division cycle moves on to metaphase. 
• During the metaphase pulling and pushing pressures, the condensation process is essential to prevent the destruction of chromosomes (chromatids).
• At the end of prophase or prometaphase, the chromosomes are randomly positioned within the cell nucleus, within a fragmented nuclear membrane.
• The polar and radial microtubules, on the other hand, are separately connected to each chromosome.
• During mitosis, centrosome microtubules attach to each chromosome, which is made up of two identical sister chromatids. Cohesins are proteins that help sister chromatids communicate with one another.
• Microtubules enable the cell to function as a dynamic organism by allowing pulling and pushing forces to be applied.
• The sister chromatids align at the cell's center, forming a metaphase plate, which is aided by the kinetochore microtubules.
• The sister chromatids' close adhering is further assisted by these treadmilling stresses.
• The alignment of the chromatids along the metaphase plate ensures that the new cells produced will be identical.
• The chromatids must be attached to the microtubules from both poles of the cell and positioned at the metaphase plate for the spindle assembly checkpoint to occur.
• The checkpoint delays metaphase, which can take days to ensure that all of the chromosomes are properly aligned.
• Following the checkpoint, the chromosomes emit a signal that activates the anaphase-promoting complex, causing metaphase to finish and anaphase to begin.
• Tubulin, a microtubule sub-unit, is constantly added and removed from the microtubules' ends. As a result, the sister chromatids and microtubules travel in a treadmilling motion.

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 Applications of Metaphase

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• During the metaphase stage of the cell cycle, karyotyping can be used to detect genetic abnormalities. 
• Cross-overs (meiosis) occur during this phase, and the pulling and pushing of chromatids by the kinetochore microtubules can cause chromosome damage if the mitotic spindle checkpoint and the meiotic spindle checkpoint are missed.

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Things to Remember

• Mitosis is the process through which one cell divides into two identical daughter cells (cell division). Mitosis is the process that allows cells to proliferate and replace themselves.
• The replicated chromosomes line up in the centre of the dividing cell during metaphase.
• The equatorial plate, also known as the metaphase plate, is the stage of cell division in which the duplicated chromosomes align themselves along the cell's centre.
• During the metaphase pulling and pushing pressures, the condensation process is essential to prevent the destruction of chromosomes (chromatids).
• Metaphase lasts up to an hour and is followed by mitosis and meiosis' second division, during which the paired chromosomal strands (called chromatids) are separated.
• Every cell in the organism undergoes mitosis, with the exception of germ cells, which are formed through meiotic cell division.

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Previous Year Questions

• Dissolution of the synaptonemal complex occurs during:…..[NEET 2020]
• During gamete formation, the enzyme recombinase participates during...[NEET 2012]
• During mitosis, ER and nucleolus begin to disappear at...[NEET 2010]
• Which one of the following is the correct indication of the stage/phase in the cell cycle?...[NEET 2009]
• How many mitotic divisions are needed for a single cell to make 128 cells?...[NEET 1997]
• Identify the meiotic stage in which the homologous chromosomes separate while the sister chromatids remain associated at their centromeres...[NEET 2012]
• In a somatic cell cycle, DNA synthesis takes place in…..[NEET 1994]
• In meiosis crossing over is initiated at :….[NEET 2016]
• Some dividing cells exit the cell cycle and enter vegetative inactive stage. This is called quiescent stage (G0​). This process occurs at the end of :...[NEET 2020]
• Which of the following options gives the correct sequence of events during mitosis ?...[NEET 2017]
• A bivalent of meiosis I consists of….[KCET 2013]
• Cells in the quiescent stage (G0​)...[KCET 2019]
• The microtubules from opposite poles of spindle get attached to the kinetochores of sister chromatids in...[AMUEEE 2009]
• Cell cycle includes the sequence….[AMUEEE 2014]
• Chiasmata formation takes place during...[AMUEEE 2010]