Mitosis

Mitosis is simply defined as eukaryotic cell division. This definition can be split into two separate but equally important portions. Cell division is the method by which cells, the simplest unit life, proliferate. Eukaryotic, in the definition of mitosis, refers to a type of cell that is manifested in living organisms in the Domain Eukarya. The adjective, eukaryotic, is essential in defining mitosis, as without it, this would be binary fission, the prokaryotic cell division undertaken by those in the Domains Prokarya and Archaeobacter. The main difference between prokaryotic and eukaryotic cells would be the existence of a true nucleus in the Eukarya, as well as inner cellular membranes, while Prokarya have closed, circular, and covalently-bonded DNA, resulting in a much simpler version of cell division.
Mitosis is actually the shortest portion in the cell cycle, the rest of which is spent in Interphase: the portion of the cell cycle performs its functions, gains volume and mass, creates new proteins and materials for DNA synthesis and duplicates its DNA. While mitosis is continuous, scientists have managed to identify four main phases in this process: Prophase, Metaphase, Anaphase and Telophase.
In prophase, the chromatin fibers in the nucleus condense and become readily visible as individual chromosomes. These chromosomes were already duplicated in Interphase, now the twin chromosomes, known now as chromatids, pair up around a centromere. Microtubules, the mechanism by which the twin chromosomes will later be pulled apart into the resulting daughter cells, are formed from the centrosomes, both of which begin to drift to opposite poles of the cell. These attach to the centromeres of the joined twin chromosomes, forming a mitotic spindle. The nuclear lamina are also broken down and separated, causing the dissolution of the nuclear membrane.
At metaphase, the mitotic spindle is fully formed and the chromosomes’ centromeres are aligned along the center of what is known along an imaginary line between both centrosome poles. This line is also known as the metaphase plate. Because of the way the chromosomes are oriented, when the kinetochores are pulled on by the microtubules, each of the daughter cells will have an exact replica and equal number of each chromosome. Anaphase occurs when the twin chromatids’ centromeres detach and begin being pulled towards their respective, opposite poles. It is at this point that the chromatids are known as ‘daughter chromosomes’ and the microtubules attached to their individual kinetochores begin to shorten to aid their delivery to their respective cells.
The last stage of the mitosis involves telophase and cytokinesis. In telophase, the chromatin fibers begin to relax uncoil back into their forms at the start of prophase. Daughter nuclei and nucleoli begin to form; the nuclear laminae begin to take shape around the chromosomes. This results in the accomplishment of the purpose of mitosis: two identical daughter nuclei are divided from one, original and genetically identical nucleus. It is only when the mitotic spindle dissociates completely that telophase is considered over. Cytokinesis is the process by which the cellular membrane and the cytoplasm begin to divide in half. This usually occurs simultaneously with telophase, and results not only with two identical daughter nuclei, but also with two identical daughter cells with roughly the same volume, and the exact same genetic structure.