MITOSIS

Mitosis or mitosis, the process of splitting the nucleus of somatic cells (not sex) whose result is the exact division of the genetic information that previously had doubled during interphase of the cell cycle. Mitosis ensures that the number of chromosomes in the cells remains constant from generation to generation. The progenitor cell gives rise to two daughter cells, genetically identical to the mother, which contain a diploid number of chromosomes characteristic of the species.
Multicellular organisms need to thrive mitosis, cells grow and replace damaged tissues or organs. All these agencies come from a single cell. This cell is multiplied through successive cell divisions that include processes of mitosis (division of the nucleus) and cytokinesis (division of cytoplasm), which lead to the development of complex organisms composed of trillions of cells. These processes also remain active throughout the life of the organism, which allows cells to replace damaged, diseased or dead. In the human body produces about 25 million per second mitosis.
Single-celled organisms reproduce asexually, resulting in offspring that are identical to the parent body. In addition, certain multicellular organisms such as starfish or sea anemones, are dependent on mitosis, at certain stages of their life cycle, to reproduce asexually.
2 THE CELL CYCLE AND CELL DIVISION
The cell cycle comprises a series of ordered phases. During these phases, the cell duplicates its contents and divides into two daughter cells. The cell cycle of a eukaryotic cell, ie a cell with a nucleus, consists of two periods: interphase and mitotic phase (M).
Interphase is the longest period of the cycle and is a step prior to cell division. During interphase, the cell duplicates its deoxyribonucleic acid (DNA) and produces cytoplasmic organelles and other components. The interface comprises three stages: G1, S and G2.
During the mitotic or M phase the cell divides. The mitotic phase involves splitting the nucleus (mitosis proper) and cytoplasmic (cytokinesis) and involves the equal distribution of cellular material between the two daughter cells.
3 THE MITOSIS OR DIVISION OF THE NUCLEUS
Mitosis, or division of the nucleus is the process by which DNA, which has doubled during interphase, separated in two sets of chromosomes that are distributed in each of the nuclei of future daughter cells.
4 phases of mitosis
Although mitosis or division of the nucleus is a continuous process for study differ in several stages: prophase, metaphase, anaphase and telophase.
4.1 Prophase
At the beginning of prophase chromatin fibers (DNA and proteins) are condensed, shortened and visualized under a microscope as small rods that are called chromosomes. As a result of DNA replication during interphase, each chromosome containing a pair of identical chromatids joined by a region called the centromere. Then, the nucleolus disappears and the nuclear membrane begins to fragment. The centrioles, two structures located in the centrosome, split each in migrating an opposite pole of the cell, while the mitotic spindle form or achromatic. The mitotic bone is a structure formed by microtubules that are arranged in an ovoid shape and extending between the centrioles to push toward the poles to grow. The primary function of centrioles is the formation and organization of microtubules, proteins that form the mitotic spindle.
4.2 Metaphase
In metaphase, the chromatid pairs are aligned right in the center of the spindle apparatus (or equatorial plane of the metaphase) by action of the spindle fibers, which are joined together by the centromeres. Each chromosome is displayed with an X in the central plane of the cell.
4.3 Anaphase
During anaphase, the centromeres divide, allowing each of the identical chromatids pair is separated (chromosomes children) and are routed to the two poles of the cell carried by the spindle microtubules. In this shift, the chromosomes acquire a V as the centromere, pulled by the microtubules, moves the first. The set of chromosomes from one pole of the cell is identical to the other pole. Each one of them, form the chromosome of each of the two daughter cells.
4.4 Telophase
The final phase is telophase of mitosis. During telophase, each set of chromosomes is unrolled and converted back into chromatin. Each chromatin mass is surrounded by a nuclear membrane in each new nucleus is a nucleolus and the mitotic spindle disappears.
5 cytokinesis
Coinciding with the end of anaphase or early telophase also begins the cytokinesis or division of the cytoplasm.
In animal cells, cytokinesis begins with the appearance, up to half of the cell, a dividing groove perpendicular to the spindle apparatus. This groove progressive advances producing a bottleneck that eventually leads to the physical division of the cytoplasm and thereby to the formation of two daughter cells with their corresponding cores. In plants, cellulose and other materials transported to the midline of the cell, where they form a new cell wall (fragmoplasto) separating the two new cells. The daughter cells enter interphase, restarting the cell cycle.
In multicellular organisms, mitosis and cytokinesis are controlled primarily by cellular proteins. The duration of the mitotic phase and cytokinesis depends on cell type and can last two hours or even a few minutes. The process of mitosis ensures that all progenitor cell genes passed on to daughter cells. However, errors sometimes arise in DNA replication or mitosis itself, which can lead to changes or mutations in genes that have not been copied correctly or unequal distribution of chromosomes.