Mitosis, Meiosis and their Regulation

How Does Mitosis Work

At the level of individual cells, reproduction is driven by the process known as cell division. With the exception of germ cells, most eukaryotic cells divide in such a way that the ploidy, or the number of chromosomes, stays the same. Germ cells, on the other hand, divide in such a way that the number of chromosomes is cut in half.

Mitosis is the phase of the cell cycle in which the nucleus of a cell is divided into two nuclei with an equal amount of genetic material present in both of the daughter nuclei. This occurs during the division phase of the cell cycle. It comes after the G2 phase and is followed by cytoplasmic division after the nucleus has been separated from the rest of the cell.

Characteristics of Mitosis

• During each cycle of cell division, the parent cell gives rise to two new cells that are known as daughter cells
• Due to the fact that the number of chromosomes in both the parent cell and the daughter cell remains the same, this type of cell division is also known as equational cell division
• In plants, the process of mitosis is responsible for the formation of new vegetative parts, such as the root tip, stem tip, and so on
• During this procedure, neither segregation nor combination will take place

The mechanisms that take place during mitosis have been broken down into a number of distinct stages.

The Mitotic Stages

The majority of the cell’s lifetime is spent in the interphase, which is immediately preceding prophase. During this phase, the cell makes the necessary preparations for the beginning of mitosis (the DNA is copied). Prophase is technically the first stage of this process; however, because the actual process requires the division of the nucleus, it is not considered the first stage.

The following is a list of the several stages of mitosis that take place throughout the process of cell division:

Interphase

Interphase is the stage of a cell’s life cycle that occurs before it enters the mitotic phase of its cycle. When it is in the interphase state, it goes through the following phases:

The G1 Phase is the stage of cell division that occurs before the production of DNA.

DNA synthesis takes place at this stage of the process, referred to as the S Phase.

The G2 Phase is the phase that occurs between the completion of DNA synthesis and the start of the prophase of the cell cycle.

Prophase

Condensation of the genetic material occurs during prophase, which comes immediately after the S phase and the G2 phase of the cell cycle. This results in the formation of compact mitotic chromosomes, which are made up of two chromatids that are attached at the centromere.

The completion of prophase is characterised by the beginning of the assembly of the mitotic spindle, the microtubules, and the proteinaceous components of the cytoplasm that help in the process. This occurs simultaneously with the formation of the chromosomes.

When this happens, the nuclear envelope begins to fall apart.

Prometaphase

The nuclear envelope starts to fall apart during the prometaphase of the cell cycle. After this step, the microtubules are given permission to expand all the way from the centromere to the chromosome. It is possible for the cell to move the chromosome around because the microtubules link themselves to the kinetochores.

Metaphase

At this point, the microtubules begin pulling with equal force on the chromosomes, and the chromosome eventually finds its way into the middle of the cell. The name “metaphase plate” refers to this particular location. This results in each cell having its own fully functional genome.

Anaphase

The beginning of anaphase can be identified by the separation of the sister chromatids. The chromosomes of the daughter nuclei are made up of these sister chromatids when the cell divides. After this, the fibres that are connected to the kinetochores of each chromosome begin to tug the chromosomes in the direction of the pole. Each chromosome’s centromere is located at the front edge, while the arms of the chromosome trail behind it.

Telophase

As the nuclear membrane begins to form around it, the chromosomes that cluster at the two poles begin to condense into a single, undifferentiated mass. After prophase, structures such as the nucleolus, Golgi bodies, and ER complex vanished. Now, however, they begin to reappear.

The Roles Mitosis Plays in the Cell

The two most significant roles that mitosis plays are as follows:

• Mitosis is an important process that contributes to the development of an organism. Mitosis is the process of asexual reproduction that occurs in organisms composed of a single cell
• Mitosis contributes to the process of replacing tissues that have been destroyed. When the cells in the vicinity of the injured cells are unable to detect their neighbours, this triggers mitosis in those cells. The cells that are dividing reach each other and cover the ones that are injured

Meiosis Overview

Meiosis is a type of nuclear cell division that results in daughter cells that have one-half the number of chromosomes as the original cell. These daughter cells inherit their chromosomes from their mother cell.

The final product of the process of cell division in diploid organisms is the formation of haploid cells. Each daughter cell inherits one full set of chromosomes, meaning that it receives one copy of each of the homologous chromosome pairs.

In humans, this results in a reduction from 46 to 23 of the total number of chromosomes.

Meiosis is the process that gives rise to both sperm and eggs from the germ cells.

When a sperm and an egg combine to form a fertilised egg, the number of chromosomes in the egg is restored to its original count of 46.

Due to the fact that cells that go through meiosis also go through the rest of the cell cycle, including the S phase, the process starts with chromosomes that are made up of two chromatids, just like mitosis does.

Meiosis is broken up into two distinct stages: meiosis I and meiosis II. During the first stage of meiosis, homologous chromosomes are partitioned off into their own distinct nuclei.

This is known as the reduction division, and it involves halving the total number of chromosomes. Meiosis II is extremely similar to mitosis in that the chromatids split off into their own nuclei at this stage.

The chromosomes and chromatids are “pulled” away from one another in meiosis by spindle fibres, much as they are in mitosis.

Conclusion

Meiosis results in the production of four cells, each of which has one complete set of chromosomes as opposed to the two sets of chromosomes that were produced during mitosis.

Mitosis is responsible for the repair and regeneration of damaged tissues and is necessary for asexual reproduction and vegetative proliferation in plants.

The process of mitosis is necessary for the continuation of cell growth as well as the regeneration of old, damaged cells. Abnormalities that occur during mitosis have the potential to change the DNA, which can then lead to genetic diseases.