A Dr. and a patient experiencing trouble with skin-repairing from a cut, and is expecting a child, the cell is malfunctioning in the cell division

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Types of cell division and stages involved

The body has its mechanism of repairing and maintaining its tissues. This mechanism is referred to as cell division. It occurs when dead and worn-out cells need to be replaced, for instance when repairing a skin cut or a healing wound. Another reason for cell division is to facilitate the growth of organisms. Cell division is classified into two categories – mitosis and meiosis. Mitosis is a type of cell division that ensures the growth, repair, and maintenance of body organs and tissues. On the other hand, meiosis is involved with sexual reproduction where the divided cell has half the number of chromosomes.

Mitosis

This is the cell division of non-reproductive cells. It occurs when the body needs to repair and maintain its tissues and organs. The dividing cell is referred to as the “parent cell” while the cells resulting from the division are referred to as “daughter cells”. In this type of cell division, the daughter cells inherit the same number of chromosomes and DNA composition as the parent cells. The daughter cells that result from the division are referred to as diploid cells. Mitosis involves several stages that lead to a successful cell division as outlined below.

The first stage is the prophase stage where chromosomes of the cell condense and are visible. The nuclear envelope of the cell breaks and spindle fibers start forming from the centrosomes. At this stage, the centrosomes start moving towards the opposite poles of the cell. The second stage is the prometaphase stage where chromosomes keep on condensing and kinetochores start appearing at centromeres attached by the spindle fibers. The third stage is the metaphase stage where chromosomes align at the metaphase plate. Spindle fibers originating from opposite poles connect sister chromatids. The fourth phase is the anaphase stage where the splitting of the centromeres occurs and chromosomes move towards the opposite poles of the cell. The cell starts to elongate due to the spindle fibers. The fifth stage is the telophase stage where a nuclear envelope encircles each of the two sets of chromosomes. Also, spindle fibers begin to breakdown at this stage while pushing poles apart. The final stage in cell division is cytokinesis where the daughter cells divide into two separate cells.

Meiosis

The main purpose of this type of cell division is to produce sex cells. The daughter cells from this division have half the number of chromosomes of the parent cells. At the end of the division process, a diploid parent cell ends up being a haploid daughter cell. During reproduction, two haploids from both male and female join together to form a diploid set with complete chromosomes. Meiosis involves a two-step division process-meiosis I and Meiosis II. In meiosis I, the cell undergoes four interphase stages namely prophase I, metaphase I, anaphase I, and telophase I. In prophase I, homologous chromosomes exchange parts during a cross-over process. This facilitates the trading of genetic material between the sister chromatids. In the second stage, metaphase I, homologous pairs of chromosomes align at the metaphase plate to facilitate separation. In the third stage, anaphase I, homologous pairs separate and move to the opposite ends of the cell. The final stage is the Telophase I stage where chromosomes move to the opposite poles of the cell and two haploid cells are formed. The process moves to meiosis II. Meiosis II follows similar stages as meiosis I but it is simpler. It is akin to the mitosis of haploid cells. The first stage is the prophase II stage where chromosomes condense and centrosomes drift apart. The second stage is the metaphase II stage where chromosomes align at the metaphase plate. The third stage is the anaphase II stage where sister chromatids drift apart to the opposite poles of the cell. In the final stage, the telophase II stage, the chromosomes are encircled by nuclear membranes and cytokinesis occurs resulting in four haploid cells.

Advantages of mitosis cell division

The resulting daughter cells have the same number of chromosomes and DNA composition hence it is most appropriate for tissue maintenance and repair.

Disadvantages of mitosis

Exact copies of the parent cells result from this type of cell division leading to limited diversity. Negative traits tend to be amplified in this case. Also, there is no chance for improved offspring as the parent genes are duplicated. 

Advantages of meiosis

Meiosis provides a variety of offspring due to the exchange of genetic material. This brings about the diversity of the genetic composition of organisms. Meiosis leads to a genetic improvement of the offspring as compared to the parents. 

Disadvantages of meiosis

It is a complex and lengthy process that consumes time and energy. 

Discussion of how cell development can be altered

A malfunctioned cell division in a pregnant woman means that the fetus will also be equally affected. This is because genetic disorders can be inherited. During meiosis, chromosomes may behave abnormally leading to genetic disorders arising from abnormal chromosome numbers and structural arrangements (Malumbres, pg. 69). These disorders are a result of nondisjunction, an impairment that occurs because of the homologous chromosome’s failure to disintegrate in the meiosis process. This could lead to monosomy (one less chromosome) or trisomy (one extra chromosome). Monosomy in embryos causes failure to develop to maturity because they lack some essential genes. Trisomy in embryos may allow it to develop to maturity but suffer from genetic imbalances. Individuals with more than the normal number of chromosomes are known as polyploids. When fertilization occurs between a polyploid and a normal haploid, the result is a polyploid zygote which is usually sterile. These disorders may lead to improper development of the unborn child both physically and mentally.

References

Salazar-Roa, M., & Malumbres, M. (2017). Fueling the cell division cycle. Trends in cell biology, 27(1), 69-81.