Cell_Div

What is cell division' Well, cell division is the process by which a parent cell divides into two or more daughter cells. The occurrence and temporariness of cell division depends on the differentiations of certain cells. For example, while skin cells divide nearly continuously after birth, some highly specialized cells, such as specific neurons, don’t and cannot be replaced after injury or death. There are two types of cell division; mitosis and meiosis. Mitosis is the process in which one eukaryotic cell divides into two cells identical to the parent cell. Meiosis is the process of cell division in sexually reproducing organisms that reduces the number of chromosomes in reproductive cells from diploid to haploid, leading to the production of gametes in animals and spores in plants. Mitosis is composed of six stages; interphase, prophase, metaphase, anaphase, telophase, and cytokinesis. During interphase, cellular organelles double, the DNA replicates, and protein synthesis occurs. During prophase, the nuclear membrane disintegrates and the nucleolus is then not visible. During metaphase, the chromosomes become attached to the mitotic spindles and then line up along the equator of the cell. In anaphase, the kinetochore microtubules shorten and sets of two daughter chromosomes shift toward opposite poles of the cell, elongating the cell. During the telophase stage, chromosomes reach the poles of the cell and start to disappear, while nucleoli begin to appear. Telophase is finally followed by cytokinesis. Cytokinesis is when a cleavage furrow forms in the core of the cell, and the cell then divides. There are two different types of meiosis; meiosis I and meiosis II. The difference between meiosis I and meiosis II is that meiosis I separates homologous chromosomes and meiosis II separates sister chromatids. Along with mitosis, meiosis also has stages. Meiosis I has four stages; prophase, metaphase, anaphase, and telophase. Prophase I is the most significant stage in meiosis I. During prophase I, chromosomes condense and therefore become invisible; the centrioles move towards the poles of the cell, and the nuclear membrane begins to dissolve. In metaphase I, the microtubules form from the centrioles and connect to the centromeres. During anaphase I, the centromeres break and cytokinesis begins. Finally, in telophase I, cytokinesis is completed creating two daughter cells. Meiosis II also has four stages; prophase, metaphase, anaphase, and telophase. During prophase II, centrioles form and move toward the poles of the cell and the nuclear membrane dissolves. In metaphase II, the microtubules attach to the centomeres and sister chromatids line up along the equator of the cell. In anaphase II, centromeres break and sister chromatids separate, cytokinesis begins. Finally, in telophase II, cytokinesis completes and creating four daughter cells. Essentially, all of the different types of cell division (mitosis, meiosis I, and meiosis II) result in the reproduction of a cell. The type of cell division that can and will be used for reproduction will depend on the organism.