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Cell Division and Cell Junctions

In the process of cell division, cells reproduce themselves through cell division. Cell division is of two types that include mitosis and meiosis.
Cell division
In the process of cell division, cells reproduce themselves through cell division. Cell division is subdivided into two types that include mitosis and meiosis.

Mitosis
Each new cell must have a diploid number to undergo mitosis since the two sets of chromosomes are necessary for mitosis. Two identical diploid cells with the same number of chromosomes are formed during mitosis when one diploid cell divides into two identical myoblasts. A chromosome can duplicate itself by way of DNA replication. The time in between the two divisions of a cell is called the interphase. It is also called as resting stage.

There are four stages of mitosis:

Prophase - The chromosomes appear as short rod-like structures. Chromosomes are made up of two copies (original DNA plus copy) that are still attached to a region known as the centromere. Eventually, the nuclear membrane vanishes. The centrioles locate themselves along opposite poles of the equator and are responsible for organizing the spindle fibers.

Metaphase - A cell's equator is lined up with chromatid pairs in metaphase. Centromeres are attached to spindle fibers in each pair. It is now time for the centromeres to divide.

Anaphase - There are now two complete sets of chromosomes, each containing a chromatid. All chromosomes are pulled toward the poles by the spindle fibers within the cell.

Telophase - When the DNA of the sets of chromosomes uncoils to form chromatin, they cease to be distinct. There is a nuclear membrane surrounding every set of chromosomes.

Meiosis
Meiosis is a more complex form of cell division, which results in gametes, the cells that produce eggs and sperm. During meiosis, one cell has diploid chromosomes and divides into four cells, each having haploid chromosomes (half the usual number). Oogenesis, the process of meiosis taking place in the ovaries, is called meiosis in women. Spermatogenesis, which takes place in men, is the result of meiosis.

Human egg and sperm cells are haploid, meaning they have 23 chromosomes. Due to the reduction in chromosome number during meiosis, the division process is sometimes called reduction division. Then by combining the 23 chromosomes in the sperm and the 23 chromosomes in the egg, the 23 chromosomes in the fertilized egg are recovered as 46 chromosomes during fertilization.

Cell junction
Animal cells connect via intercellular junctions called cell junctions between the plasma membranes. multi-protein complexes act as connective tissues between cells or function as a means of establishing contact between cells and the extracellular matrix.
There are three types of cell junction:

Tight junction: Tight junctions are formed by two epithelial cells fusing which act as a barrier, preventing fluid from passing between cells.

Gap junction: In a gap junction, neighboring cells are connected by an intercellular channel that allows direct communication between them. Ions, molecules, and electrical impulses move within cells without crossing their outsides.

Anchoring junction: Connecting junctions between cells are anchored to the extracellular matrix and attached. An anchoring junction is a desmosome, hemidesmosome, or adherent junction. They play an important role in preserving structural integrity among cells and tissues.

Conclusion
On the cytoplasmic side of the plasma membrane, there is a thick fibrous layer called the plaque. As an actin microfilament, it binds to the adherent junction, and intermediate filaments are attached to desmosomes and hemidesmosomes. A tight junction consists of tightly packed junctional proteins fused at their junctions. They are responsible for the formation of barriers between the cells by differentiation and polarisation as well as by modulating cell proliferation. They also regulate the functions of these barriers by restricting paracellular diffusion.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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