What is Cell Division? Process, Cell Cycle, Mitosis

What is cell division?

Each day, every hour, every second, one of the most important processes in life is going on in your body—the cells are dividing. As a result of the cells dividing, new cells are formed. A single cell splits into two cells, then split into four cells, and so on. This process is called “cell division” because new cells are produced due to the division of old cells.

Why does cell division occur?

The dividing of cells occurs because of many reasons. Suppose when you hurt the skin on your knee, cell division occurs so that damaged or non-functioning cells are replaced over there. Cells also divide to allow the living beings to grow. When organisms grow, it is not because the cells are getting larger. Rather, because cells are dividing to produce more and more of them. In human bodies, nearly trillions of cells divide each day.

How Do Cells Know When to Divide?

During what is cell division, the cell that undergoes division is called the “parent” cell. It divides into two “daughter” cells. The same process repeatedly occurs again in what is called the cell cycle. 

Cell division is regulated by using chemical signals from special proteins called cyclins to communicate with each other. These signals function like switches to instruct the cells about when to start dividing and when to stop. The process of diving into a cell is important so you can grow and so your cuts heal. It is equally important for the cells to stop dividing at the right time.

If a cell cannot stop dividing when it is supposed to, it can lead to a life-threatening disease called cancer. The lack of control over the growth of these cells prevents them from repairing their DNA effectively, giving rise to aberrant mitosis, resulting in mutations that prevent the cells from remaining in their tissues of origin as they normally do. For example, cancerous epithelial cells acquire the ability to cross the basal lamina and infiltrate the bloodstream of the lymphatic network, through which they migrate to other body parts. This process is called metastasis. The tumours that metastasise to distant tissues are termed malignant, while those that don’t are described as benign.

Some normal cells, like skin cells, are continuously dividing. We must continuously produce new skin cells to replace the old ones we lose. It will be surprising for you to know that we lose 30,000 to 40,000 dead skin cells every minute. A lot of skin cells need to be replaced, making the dividing of cells in the skin very important. Other cells of the body, like neurons or brain cells, divide much less often.  

How long does the cell cycle last?

The cell cycle duration is about 10-20 hours in rapidly growing adults. However, it can be arrested for several weeks or even months in inactive cells or even for a lifetime in neurons. This type of prolonged arrest usually occurs during the G1 phase of the cell cycle. It is sometimes referred to as the G0 phase.

In some embryonic cells like those of fruit flies, the entire process of cell cycle and division occurs in only 11 minutes. In this case, G1 and G2 phases are undetectable, and mitosis alternates with DNA synthesis. The embryo of a fruit fly takes only four minutes to duplicate its DNA, while it can take several hours in the adult cells of the same species.

How Do Cells Divide?

Depending on the type of cell, they can divide in two ways—mitosis and meiosis. Each of these ways of cell division has special features. One of the chief differences between the two is that during mitosis, one cell divides into two that are copies of each other and contain the same chromosome number. This type of cell division is ideal for basic growth, repair, and maintenance. In meiosis, a cell divides into four daughter cells that contain half the number of chromosomes. Decreasing the number of chromosomes by half is vital for sexual reproduction and allows genetic diversity. 

Mitosis Cell Division Definition

Mitosis is the process by which non-reproductive cells undergo division. What are somatic cells? Well, somatic cells make up most of your body’s tissues and organs, including your skin, muscles, gut, lungs, and hair cells. Reproductive cells are different from somatic cells.

In mitosis, the important point to remember is that all the daughter cells have the same chromosomes and DNA as the parent cell. The cells produced as a result of mitosis are referred to as diploid cells. They have two full chromosome sets. Since the newly formed cells have the same DNA as that of the parent cell, no genetic diversity is generated through mitosis in normal healthy cells. 

The Mitosis Cell Cycle

Before a cell starts dividing, it is said to be in the “Interphase.” While it seems that cells must constantly be dividing (as there are trillions of what are cell divisions in the body daily), each cell stays in the interphase for most of its time. Interphase is when a cell gets ready to divide and start the cell cycle by gathering nutrients and energy. Also, the parent cell makes a copy of its DNA to share equally between the two daughter cells.

There are a number of steps to the mitosis division cycle through which it can make the new diploid cells successfully

1. Interphase
2. Prophase
3. Prometaphase
4. Metaphase
5. Anaphase
6. Telophase
7. Cytokinesis.

When cell division occurs by the process of mitosis, some organelles split up between the two daughter cells. Suppose mitochondria can grow and divide during the interphase, so the daughter cells each get enough of these mitochondria. The Golgi apparatus, however, disintegrates before mitosis and reassembles in each of the new daughter cells. 

Meiosis Cell Division Definition

Meiosis is the other main process through which the cells divide. Through this process, reproductive cells, like female reproductive cells or male reproductive sperm cells, are produced. The most crucial thing to remember about meiosis is that each new cell contains a unique set of genetic information. After meiosis, the sperm and egg cells combine to create a new organism in a series of steps.    

The diversity in the genetic makeup of all sexually reproducing organisms is due to meiosis. During meiosis, a small part of each chromosome detaches and reattaches to another chromosome. This process is referred to as “crossing over” or “genetic recombination.” Due to this genetic recombination, the siblings made from egg and sperm cells from the same two parents can look quite different from one another.

The Meiosis Cell Cycle

The meiosis cell cycle consists of two main steps of division— Meiosis I and Meiosis II. The consequence of the meiosis process is four haploid daughter cells containing genetic information that is not similar to each other and the parent cell. 

During Meiosis I, the number of chromosomes is halved and crossing over happens. During Meiosis II, genetic information is halved in each cell’s chromosome. As a result, four daughter cells known as haploid types of cells are formed. There is only one unpaired set of chromosomes in haploid cells – half the chromosome number as the parent cell.

Before Meiosis 1 starts, the cell passes through the interphase. Like in mitosis, the parent cell utilises this time to prepare for what is cell division by assimilating nutrients and energy and copying its DNA. In the next stages of meiosis, this DNA switches around during genetic recombination and is then divided between four haploid daughter cells.

Conclusion

The division of a cell is a vital process for the maintenance of the life of all organisms. Its regulation is equally important. During the division of a cell, the DNA produces a copy of itself, which is then distributed into two daughter cells. From careful DNA replication to the final cleavage of the cell, every phase of the cell division must proceed without a hitch millions of times during the lifetime of an organism. 

Frequently Asked Questions

1. Who discovered cell division?

A 19th-century professor, Walther Flemming at the Institute for Anatomy in Kyiv, Germany, was the first person to document the details of cell division.

2. What is cell division in cancer cells?

The cells in your body are continuously dividing. According to the cell division definition, healthy cells divide in a carefully controlled manner, proceeding with division only under appropriate conditions. On the other hand, cancer cells divide in an unregulated, uncontrolled manner. This leads to the accumulation of the cells, leading to a tumour. 

3. What are the phases of interphase?

• G0/ resting phase: During this phase, the cells neither divide nor prepare for division.
• G1/ gap phase: The metabolic activity of the cell is going on during this phase and grows continuously.
• S/ synthesis phase: DNA replication or synthesis occurs during this phase.
• G2/ gap 2 phase: Protein synthesis occurs.
• G0/ quiescent phase: Some cells do not undergo further division; rather, they leave the G1 phase and enter an inactive stage, known as the quiescent stage of the cell cycle.