Mitosis and it's significance

Mitosis and its significance

A cell prepares for cell division by replicating its chromosomes, segregating them, and creating two identical nuclei during the mitotic phase. The cell's contents are often evenly divided into two daughter cells with identical genomes after mitosis.Mitosis is divided into the following four stages:

1. Prophase:

Interphase's S and G2 phases are followed by prophase, the initial step of mitosis. The newly synthesised DNA molecules are not distinct but rather entangled in the S and G2 phases. The beginning of chromosomal material condensing characterises prophase. During the process of chromatin condensation, the chromosomal material is untangled. The centriole, which underwent duplication during interphase's S phase, now starts to migrate in the direction of the cell's opposing poles.Thus, the following distinctive occurrences can indicate the end of prophase:

• Compact mitotic chromosomes are created when chromosomal material condenses.Two chromatids are observed to be joined together at the centromere to form chromosomes.

• The beginning of the mitotic spindle's construction, the microtubules, and the proteinaceous elements of the cell cytoplasm aid in the process.

• The golgi complex, endoplasmic reticulum, nucleolus, and nuclear envelope are absent from cells near the end of prophase when they are observed under a microscope.

2. Metaphase:

The second phase of mitosis begins when the nuclear envelope completely disintegrates, and as a result, the chromosomes are dispersed throughout the cell's cytoplasm. The chromosome condensation process is now complete, and the chromosomes may be seen clearly under a microscope. Therefore, this is the period at which it is easiest to study the shape of chromosomes. The two sister chromatids that make up the metaphase chromosome at this point are joined by the centromere. Kinetochore refers to a little disc-shaped structure at the centromere surface. These structures act as the points of attachment for the spindle fibres, which are created by the spindle fibres, to the chromosomes that are placed at the cell's centre.Thus, all of the chromosomes align at the equator during the metaphase, with one chromatid of each chromosome attached by its kinetochore to spindle fibres from one pole and its sister chromatid connected by its kinetochore to spindle fibres from the opposite pole. The term "metaphase plate" refers to the chromosomes' alignment plane during metaphase. Metaphase's primary characteristics are:

• Spindle fibres adhere to chromosomal kinetochores.
• Chromosomes are transferred to the spindle equator, where they are positioned along the metaphase plate and along the spindle fibres to both poles.

3. Anaphase:

Each chromosome on the metaphase plate splits simultaneously at the start of anaphase, and the two daughter chromatids, which are now known as the chromosomes of the future daughter nuclei, start to move in opposite directions. The centromere of each chromosome is at the pole and, as a result, at the leading edge, with the arms of the chromosome trailing behind as they advance away from the equatorial plate. Events that define the anaphase stage are:

• Centromeres divide, and chromatids dissociate.
• Chromatids shift to the polar opposites

4. Telophase:

The chromosomes that have reached their respective poles decondense and lose their identity at the beginning of the last stage of mitosis, known as telophase. The individual chromosomes are no longer visible, and the two poles tend to accumulate a mass of chromatin material. The essential events at this stage include: 

• Chromosomes cluster at opposing spindle poles, losing their identity as distinct elements.
• The nucleolus, Golgi complex, and ER remodel themselves
• The nuclear envelope forms around the chromosomal clusters.

Cytokinesis:

In addition to segregating duplicated chromosomes into daughter nuclei (karyokinesis), mitosis also divides the cell into two daughter cells by a separate process known as cytokinesis, marking the completion of cell division. This occurs when a furrow forms in the plasma membrane of an animal cell. The cytoplasm of the cell is split in half by the furrow, which eventually merges in the centre. Plant cells, on the other hand, are surrounded by a cell wall that is rather inextensible; as a result, they go through cytokinesis using a different process. In plant cells, wall construction begins in the cell's middle and extends outward to meet the lateral walls that already exist.The basic precursor known as the cell-plate, which symbolises the middle lamella between the walls of two neighbouring cells, is formed before the new cell wall can be fully formed. Organelles like mitochondria and plastids are dispersed between the two daughter cells during cytoplasmic division. In some organisms, cytokinesis does not follow karyokinesis, which results in a multinucleate state and the development of syncytium.

Significance of Mitosis :

Only diploid cells often undergo mitosis, also known as equational division. However, haploid cells can also divide through mitosis in some lower plants and social insects. Understanding the importance of this division in an organism's life is crucial. Typically, mitosis produces daughter cells that are diploid and have the same genetic makeup. Mitosis is responsible for multicellular organisms' growth. The ratio of the nucleus to the cytoplasm is disturbed as a result of cell expansion. Therefore, cell division is required to re-establish the nucleo-cytoplasmic ratio. Cell repair is one of mitosis' most important functions.Blood cells, stomach lining cells, and the outermost layer of the epidermis all undergo continuous replacement. Plants grow continuously throughout their lives as a result of mitotic divisions in the meristematic tissues known as the apical and lateral cambium.