Cell Division - Mitosis, Meiosis1 and Meiosis2.
Mitosis defined: is nuclear division that produces two daughter nuclei, each with the same number and kinds if chromosomes as the parental nucleus. Mitosis is one of the stages in the life cycle of a cell. Mitosis is the common type of nuclear division that occurs in growth and repair of the body. Humans begin life as a single cell but eventually have one hundred trillion cells as an adult, due to mitosis. Most of mitosis cell division in adults occurs in tissues such as the epidermis of the skin, the lining of the digestive and respiratory tracts, and the lymphoid tissue that produces blood cells.
Mitosis is the process by which the contents of the eukaryotic nucleus are separated into two genetically identical packages. Chromatin is condensed into chromosomes and centosomes have duplicated prior to the beginning of mitosis during G2 of interphase. Mitosis is divided into four stages, prophase, metaphase, anaphase, and telephase.
During early prophase, chromosomes are duplicated. As mitosis begins, chromosomes condense, they become visible under a light microscope. They appear as sister chromatids joined at the centromere. The number of centromeres is the same number of chromosomes in a cell. Centrosomes begin moving apart as the nuclear envelop disintegrates and the nucleolus begins to disappear. Spindle is in the process of forming in late prophase. This is when the centromeric spindle fiber of microtubules forms and kinelochores of chromosomes are attaching to kinelochore spindle fibers. Chromosomes do not have a particular orientation yet.
Metaphase is the stage of mitosis when the fully formed spindle consists of poles, asters, and fibers. Centrioles may help organize the spindle as in an animal cell. The chromosomes begin to move toward the metaphase plate (equator, midplane) of the spindle. Once on the equator, the centromeres attach to the centromeric spindle fibers, and the centromeres uniting the sister chromatids divide.