How Many Types of Cell Division are There

Introduction

Cells are the basic unit of an organism. A number of cells come together to form a tissue. A number of tissues come together to form an organ, and a group of organs form an organism.

In order to form this organism, cells need to undergo various divisions to multiply enough to form a complete being.

Types of Cell Division

The process by which these cells are divided is called cell division. Based on where the process is occurring and to what end, cell division can be of two types- Mitosis and Meiosis.

1. Mitosis - Mitosis occurs when a cell undergoes the duplication in its chromosomes and divides to produce two identical daughter cells.

2. Meiosis - Meiosis occurs when cell division occurs in the male and female gonads. Here, one mother cell divides to form four daughter cells.

Mitosis

All the cells inside a human body undergo mitosis, except the male and the female gametes. The whole process is broadly divided into two phases -

1. Interphase

2. M phase (mitosis)

3. Interphase

It occurs at the interval between two mitosis phases. During this phase, the cell undergoes growth and DNA replication as it prepares for the next M phase.

Interphase is further divided into 3 phases-

• G1 phase - Cell growth occurs in this phase.

• Synthesis phase - The DNA contained inside the cell is duplicated.

• G2 phase - Protein is synthesised in the cell as the cell continues to grow in size.

2. M phase (mitosis)

During this phase, the DNA matter condenses to form chromosomes and ends up getting divided equally amongst the daughter cells. M phase is further comprised of four stages or phases-

• Prophase - The first stage of the M phase is marked by the disappearance of major cell organelles inside the cell to give space for mitosis to occur. The chromosomes start to align themselves at the centre of the cell as they move into the next stage.

• Metaphase - The second stage of the phase is marked by the alignment of the chromosome at the centre of the cell. These chromosomes are held by spindle fibres radiating from either end of the cells which latch onto the kinetochores of their centromeres.

• Anaphase - In the third stage of the phase, the chromosomal pairs are broken down as each chromatid from a pair is pulled to separate ends of the cell by the spindle fibres.

• Telophase - This is the last stage of the M phase. It is marked by the reappearance of major cell organelles around the divided chromatids and the condensation of half of the cytoplasm around either of the prospective daughter cells.

M phase is followed by cytokinesis which divides the cell into two identical daughter cells.

Meiosis

Occurring in the reproductive organs of males and females, meiosis is the process by which the male and female gametes (sperm and ovum) are formed.

It is divided into two phases -

1. Meiosis I

2. Meiosis II

Meiosis I is divided into 4 phases-

• Prophase I - This is the first phase of this process and is further subdivided into 5 stages:

1. Leptotene - The DNA starts condensing to form chromosomes.

2. Zygotene - Homologous chromosomes come together to form a tetrad and form a structure like synapses.

3. Pachytene - The non-sister chromatids of homologous chromosomes move closer together to exchange genetic material and stay connected at the synapses.

4. Diplotene - The chromosomes start to break free from the synapses while staying joined at the point of exchange of DNA material. This is called a chiasma.

5. Diakinesis - This stage is marked by the breakage of chiasma as the chromosomes start attaching to the spindle fibres.

• Metaphase I - Marked by the alignment of chromosomes at the equatorial plane.

• Anaphase I - Marked by the separation of homologous pairs by the contracting of spindle fibres.

• Telophase I - Marked by the reappearance of major cell organelles and is followed by cytokinesis to produce two daughter cells.

Meiosis I is followed by Meiosis II. This phase is also divided into 4 stages -

• Prophase II - Starts with the recondensation of DNA to form chromosomes.

• Metaphase II - Chromosomes align themselves on the equatorial plane of the cell.

• Anaphase II- Attached by spindle fibres, each chromatid from a chromosome is pulled to opposite ends of the cell.

• Telophase II - Marked by the reappearance of cell organelles and the decondensation of DNA. This stage is followed by cytokinesis to give rise to four daughter cells.

Difference Between Mitosis and Meiosis

Conclusion

Two types of cell division occur in the human body. These are mitosis and meiosis. Mitosis is a four-stage process which produces diploid identical cells to contribute to the growth and repair of the body. On the other hand, meiosis is an overall eight-stage process which leads to the production of human gametes (sperm and ovum).

It is via these two processes that the human body ensures our well-being and the reproduction of progeny.