The process of cell reproduction involves cell division, whereby how parent cells divide into two or more cells. During this process, the parent cells duplicate their contents and then split to yield similar cells with the same contents (Arizona State University, 2014). The cell reproduction processes are cell mitosis and cell meiosis.
Cell Mitosis
Cell mitosis refers to the division of the nuclei of cells. Cell mitosis happens when the parent cell splits to produce two similar daughter cells. The replicated chromosomes are divided into two new nuclei. Hence, cell mitosis produces genetically similar cells with an equal number of chromosomes (Arizona State University, 2014). The process of cell mitosis stages as discussed below.
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The prophase is the starting stage of the mitosis cell division. During this phase, the chromosomes start undergoing the condensation process. The condensation process continues in the next stage, the metaphase. During this phase, the removal of cohesin from sister chromatids' arms allows resolving sister chromatids individually (Brachet & Mirsky Eds., 2014). However, the cohesion is entirely removed as some are maintained in the centromere, which is the most constricted part of the chromosome. Additionally, the spindle starts forming when centriole pairs begin to move to opposite poles. Besides, during this phase, the microtubules start polymerizing from the duplicate centrosomes.
The second phase, prometaphase, starts with a rapid disintegration of the nuclear membrane into numerous vesicles that divide into the daughter cells at the end. The deterioration of the nuclear cover is vital in the spindle's assembly since it gives the spindle access to the chromosomes (Brachet & Mirsky Eds., 2014). In addition, the microtubules rapidly disassemble and assemble and develop out of the centrosomes. They also seek to attachment to the chromosomes' kinetochores. The prometaphase also ensures that chromosomes are tugged in different directions by the microtubules extending from spindle poles.
After the prometaphase, the cell division process enters the metaphase. It is during metaphase that the chromosomes become visible to cytogeneticists. This phase serves as the checkpoint since complex mechanism decides if the spindle is assembled correctly and allows only the cells with well-assembled spindles to proceed to the anaphase.
The abrupt separation of sister chromatids marks the anaphase, and the reason for the break is the degeneration of the cohesion that joins the chromatids. The anaphase takes place in two parts. In the first stage, the microtubules' kinetochores become shorter, while the chromosomes start travelling to the spindle's poles (Brachet & Mirsky Eds., 2014). In the second part, the spindle poles separate as the non-kinetochore microtubules travel past each other.
The telophase is the final phase of the cell mitosis process. During this phase, the chromosomes get to the poles. The nuclear reforms and chromosomes' membrane starts de-condensing into their interphase conformations (Brachet & Mirsky Eds., 2014). The cells then divide into two daughter cells that have identical genetic compositions.
Cell Meiosis
Cell meiosis results in the production of the gametes, sex cells (sperms and eggs). The goal of cell meiosis is to produce cells with halve the chromosomes contained in the original cells (Arizona State University, 2014). Cell meiosis is comparable to cell mitosis in that the cells undergo similar stages and use replica strategies in organizing and separating the chromosomes. However, the process is more complex in the cell meiosis process since, in addition to separating sister chromatids, the chromatids must be similar but non-identical (Brachet & Mirsky Eds., 2014). The process of cell meiosis occurs in two phases, Meiosis I and Meiosis II. It is complex because, during each phase, the cell undergoes the prophase, metaphase, anaphase, and telophase stages.
Meiosis I
The meiosis I phase starts with the prophase I stage. At this stage, the chromosomes begin to condense while pairing up. The homologous chromosomes exchange parts through a process called crossover. The crossover process is aided by the synaptonemal complex, a protein structure that holds together the homologs (Brachet & Mirsky Eds., 2014). After the crossover process, the spindle begins capturing the chromosomes and moving them to the cell's center. The chromosomes attach to the microtubules from a single pole. When the homologous chromosomes line up in this stage, their orientation is random. The homologous pairs then pull apart and move towards opposite sides of the cell while the chromatids stay attached to each other in the anaphase I stage (Brachet & Mirsky Eds., 2014). In the telophase I stage, the chromosomes reach the cell’s opposite poles.
Meiosis II
The cells that enter the meiosis II phase are haploid, meaning that they have just one chromosome from each homolog pair, although they still contain two sister chromatids. During the prophase II stage, the chromosomes condense, and the nuclear membrane disintegrates. The centrosomes separate, leading to the formation of a spindle in between (Brachet & Mirsky Eds., 2014). Microtubules from opposite poles of the spindle capture the two sister chromatids of each chromosome. In the metaphase II stage, individual chromosomes line up along the metaphase plate. In anaphase II, sister chromatids pull apart towards the cell's opposite poles (Brachet & Mirsky Eds., 2014). The final stage, telophase II, involves forming nuclear membranes around each chromosome set and condensation of the chromosomes, which then split into new cells.
Advantages and Disadvantages of Each Type of Cell Division
The advantages of the cell mitosis process are that it creates exact copies of the original cells, which allows the development of organisms with identical properties, it enables growth and replaces the old or worn-out cells, and that it enables organisms to fight diseases and aids the healing process (Brachet & Mirsky Eds., 2014). Its disadvantages are that it does not promote diversity. It increases the risk of extinction as its products are similar to the parent cells. It does not encourage adaptation to changes in the environment by the offspring.
On the other hand, the advantages of meiosis are that it is a method of self-induced cloning; offspring of cell meiosis is more likely to survive and adapt as they have a different DNA. It encourages diversity and can result in more complex organisms (Brachet & Mirsky Eds., 2014). Its disadvantages are the process is complex, it is also a slow process that can take up to a year in some organisms, and that a malfunction in the can result in an offspring with adverse characteristics.
How Cells development alters Haploid and Diploid Cell Development
Stopping bleeding in the mother involves thrombocytes that are a significant clotting factor in homeostasis. Once the wound is closed with a clot, blood vessels then allow blood with oxygen and nutrients to flow to it for healing. The process of cell mitosis promotes rebuilding the area damaged by the wound (Brachet & Mirsky Eds., 2014). As such, for the patient who is experiencing problems with cell repairs, it means that the process of cell mitosis is a malfunction, and that is why the cells are unable to repair themselves. Also, for the patient with problems with reproduction cells malfunction, the malfunction can potentially alter haploid and diploid cells' development. While haploid cells have a single chromosome set, meaning they do not have homologous chromosomes, the diploid cells have two sets of chromosomes, meaning they have two homologous chromosomes in each cell (Brachet & Mirsky Eds., 2014). A malfunction in cell division can result in mistakes in the replication and separation of the chromosomes during cell division checkpoints that can alter the development of the haploid and diploid cells resulting in mutations, gene impairment, or even tumors.
References
Arizona State University (2014). Building Blocks of Life. Arizona State University . https://askabiologist.asu.edu/cell-division
Brachet, J., & Mirsky, A. E. (Eds.). (2014). Meiosis and Mitosis: Biochemistry, Physiology, Morphology (Vol. 3). Elsevier.
