What is Cell Division And Its Phases: Mitosis And Meiosis

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In this article, we will share detailed information about cell division and its phases including mitosis and meiosis. And if you are interested in more articles, comment to us below.

Cell Division:

Cell division is a process through which the parent cell divides to produce the daughter cells. Basically, all the living multicellular organisms develop from a single cell. In the case of the human body, each cell has 23 pairs of chromosomes (46 chromosomes). Out of these 23 pairs of chromosomes, 22 pairs are autosomes and the remaining 1 pair includes sex chromosomes that are in females it is XX chromosomes and in males, it is XY chromosomes.

The changes involved in the transformation of a single parent cell to multicellular living organisms are the processes of cell division and cell differentiation.

Go Phase:

G0 or G zero phase is usually referred to as a resting phase of the cell cycle in which the cell is neither involved in division nor preparing to divide, hence it is called the quiescent stage of the cell cycle.

Interphase:

Interphase is the stage of the cell cycle in which the cell is preparing for the process of cell division. It is basically divided into three phases like G1, S, and G2.

G1 Phase:

G1 phase of interphase is the major step for the process of cell division as the decision for the cell division to take place is confirmed in this phase. During this phase, the cell there are no changes in the normal functions of the cell.

S Phase:

S phase of interphase involves duplication of the DNA material. In this phase, the double helix structure of the DNA molecule separates where the two strands tend to synthesize their complementary strands and forms two new DNA double helix structure that is helpful to produce the new daughter cells in the cell division.

G2 Phase:

The G2 phase of interphase leads to the expansion or increase in the volume of the cytoplasm of the cell involved in the process of cell division.

Mitosis:

Mitosis is the process in which the parent cell divides to form two identical daughter cells containing an equal number of chromosomes as that of a parent cell. Hence, it is also known as equational cell division.

Prior to the phase of mitosis, there is a phase of interphase that is responsible for the decision and preparation for the process of cell division.

Mitosis is divided into four phases:

• Prophase
• Metaphase
• Anaphase
• Telophase

Prophase:

In this phase, the centriole present in the cell move and forms poles of the mitotic spindle. The chromosomes are formed by the condensation of chromatin material. Each of the chromosomes is made from four chromatids linked to the centromere. The nucleoli and the nuclear membrane start to disappear in this phase.

Metaphase:

In this phase, the chromosome formed starts moving to the equator of the spindle where the centromeres and the chromatids get separated. There is a duplication of the centrioles in this phase resulting in the formation of two centrioles at each end of the pole of the spindle.

Anaphase:

In this phase, the separated chromatids move towards the opposite side of the pole with the help of spindle fibers. There is an appearance of a constriction in the middle of the cell that indicated the division of cells forming two daughter cells.

Telophase:

In this phase, the chromosomes convert to form chromatin material, and the nucleoli and nuclear membrane reappear. Also, there is the formation of new nuclei. The spindle fibers disappear and thus two daughter cells formed.

Cytokinesis:

After telophase, the cytoplasm of the parent cell divides to form two new daughter cells and this phase is termed cytokinesis means the division of cytoplasm.

Meiosis:

Meiosis is the process in which the parent cell divides and gives rise to four new daughter cells comprising half the number of chromosomes that of the parent cell. Hence, this process is also known as an educational cell division as there is a decrease in the number of chromosomes in the daughter cells compared to the parent cell.

Stages Of Meiosis:

Due to this process, there is a formation of gametes (sex cells) in the body, and gamete formation occurs in two stages:

• Meiosis I
• Meiosis II

In the first stage, there is a formation of two cells with the haploid chromosome that refers to a reduction in the number of chromosomes. 
In the second stage, the two cells divide to form four daughter cells without reduction in the number of chromosomes.

Phases Of Meiosis I:

Prophase I:

In this phase, chromatin material condenses to form chromosomes and the centrioles move apart. There is a separation of chromosomes and are attached to certain points, and in between the chromatids of separated chromosomes exchange of genetic material occurs.

Metaphase I:

In this phase, there is the movement of homologous chromosomes with the help of microtubules attached to the centromere towards the equator of the cell.

Anaphase I:

In this phase, with the help of spindle fibers, the chromosome from each homologous pair tends to move towards the opposite pole. Thus, out of 23 pairs (46), 23 chromosomes move to one pole and the remaining 23 chromosomes move to the opposite pole.

Telophase I:

In this phase, nuclei are formed, chromosomes are converted back to the chromatin material, and the spindle fibers disappear. There is a development of constriction in the middle of the cell indicating that the cell is about to divide completely.

Cytokinesis:

This is a phase where the cytoplasm of the cell divides completely giving rise to two new daughter cells.

Interkinesis:

Interkinesis is also called interphase II is the phase of the cell cycle in which the cells rest in between the stage of meiosis I and meiosis II. In this phase, there is no replication of DNA molecules.

Phases Of Meiosis II:

Prophase II:

This phase is followed after telophase I, and there is a formation of new spindle fibers at a right angle to that of the earlier one. The rest process is the same as in prophase I.

Metaphase II:

In this phase, a pair of chromatids starts moving towards the equator with the help of microtubules attached to the centromere.

Anaphase II:

Again, in this phase, out of four chromatids at the equator the two chromatids move towards the opposite poles with the help of spindle fibers.

Telophase II:

The chromatids get converted to form a network of chromatin material and new nuclei are formed in this phase. Each cell divides into two without reduction in the number and finally, there is a formation of four daughter cells from one parent cell by cytokinesis. The four cells produced have a chromosome half the number compared to the parent cell. If the parent cell has '2n' chromosomes then the four daughter cells have 'n' chromosomes.

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