The biological basis of life: Cell Division

Living cells go through a fundamental “cell cycle” process that leads to the cell division of a mother cell in which cells develop, replicate their chromosomes, and then divide to generate new cells.

It is a necessary biological activity in all living organisms to continue cell reproduction.

Cell Division

Cell division is the process through which a parent cell splits, resulting in the formation of two or more daughter cells. 

In many species, it is a necessary biological process. It is the method through which multicellular organisms develop, replenish (repair), and reproduce. Cell division is the same as reproduction in unicellular organisms.

Cell division is frequently confused with mitosis. Cell division, however, is not limited to mitosis; it also occurs in meiosis. Cell division is thus a biological process that is involved in the growth and reproduction of numerous organisms. It is a component in the organism’s cell cycle.

How does cell division occur?

Cell division is regulated by cells communicating with one another via chemical signals emitted by particular proteins known as cyclins. 

These signals function as switches, telling cells when to divide and when to stop. Cell division is required for growth and wound healing. Cells must also stop dividing at the proper time. If a cell does not stop dividing when it should, it can cause cancer.

What is the cell cycle?

The series of events that occur in a cell as it grows and divides is referred to as a cell cycle. It is also known as “cellular life.”

During interphase, a cell grows, copies its chromosomes, and prepares to divide. Following that, the cell exits interphase, enters mitosis, and divides completely. The offspring cells that form enter their interphase and begin a new round of the cell cycle.

The cell cycle is a four-stage process in which the cell grows (gap 1, or G1), copies its DNA (synthesis, or S), prepares to divide (gap 2, or G2), and divides (gap 3, or G3) (mitosis, or M, stage). 

Interphase is made up of the stages G1, S, and G2, and it accounts for the time between cell divisions. A cell “decides” whether to join the cell cycle and divide based on the stimulatory and inhibitory impulses it receives.

Stages of a cell cycle

1. A cell must first expand, reproduce its genetic material (DNA), then physically divide into two daughter cells before it may divide.
2. The cell cycle is a well-organized and predictable series of phases via which cells perform numerous functions. Because the two daughter cells can resume the process from the beginning to the end of each go-round, the cell cycle is a cycle rather than a linear pathway.
3. In eukaryotic cells, or cells that include a nucleus, the cell cycle is separated into two basic phases: interphase and mitotic (M).
4. During interphase, the cell’s DNA develops and replicates.
5. During the mitotic (M) phase, the cell divides its DNA into two groups and divides into the cytoplasm, leading to cell division and the formation of two new cells.

A single cell cycle takes about 24 hours for the majority of human cells. However, in tissues where cell renewal and replacement are constantly required, such as the lining of the gut, the process is significantly faster, requiring as little as 9 hours.

Types of Cell Division

Depending upon the type of cell, there are certain types of cell division. 

In eukaryotic cells

• Mitosis
• Meiosis 

Mitosis

Mitosis is a cell-duplication or reproduction process in which one cell produces two genetically identical daughter cells. 

Mitosis refers to the duplication and distribution of chromosomes, which are the structures that carry genetic information.

The chromosomes have been replicated, and the proteins that will form the mitotic spindle have been generated, before the commencement of mitosis. 

Mitosis begins during prophase when the chromosomes thicken and coil. The nucleolus, a spherical structure, contracts, and vanishes. The beginning of the formation of a group of fibres to form a spindle and the dissolution of the nuclear membrane signal the end of the prophase.

Duplicated DNA molecules compress into tightly packed chromosomes during prophase, while microtubules form spindles. 

In prometaphase, the nuclear envelope dissolves. During metaphase, chromosomes attached to spindles align along the cell’s equator. Sister chromatids are pushed to opposing poles of the cell during anaphase. 

At last, new nuclear envelopes form around both groups of chromosomes during telophase. Following nuclear division, the cytoplasm surrounding each nucleus separates from one another by cytokinesis, yielding two identical daughter cells.

Mitosis is critical in cell division, to life because it generates new cells for growth and replaces worn-out cells. Depending on the type of cells and the species of organism, mitosis can take minutes or hours. The time of day, temperature, and chemicals all have an impact on it.

Meiosis 

Meiosis is the process by which unique cells (sperm and egg cells) with half the normal number of chromosomes are produced.

It reduces the number of chromosomes from 23 pairs to 23 singles. The cell duplicates its chromosomes but then splits the 23 pairs so that each daughter cell has only one copy of each chromosome.

A second division in which each daughter cell is divided one more to yield four daughter cells.

Meiosis is the process by which matching (or ‘homologous’) chromosomes are separated, such that sperm and egg cells each have just one copy of each. When an egg cell fuses with a sperm cell, the resulting fertilised egg contains a complete set: two copies of each chromosome.

• Meiosis occurs in two stages: Meiosis I and Meiosis II
• Meiosis I is responsible for separating identical chromosome pairs – or ‘homologous’
• Meiosis II divides each chromosome into two copies (much like mitosis)

Conclusion

The cell cycle and cell division is the process by which cells replicate and reproduce themselves, whether in eukaryotes or prokaryotes.

 It is crucial to organisms in a variety of ways, but most importantly, it permits them to survive.

For prokaryotes, the cell cycle, known as Binary Fission, permits them to survive by dividing into two new daughter cells.

In a eukaryote, such as a dog. If the dog sustains a severe injury, it will require the cell cycle to duplicate cells to replace those that were damaged in the injury, and therefore will require the cell cycle to repair itself.

The cell cycle and cell division are critical to organisms because without it, or if it stops abruptly, life would cease to exist.