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Transcript
Cell biology Mitosis Mitosis is the process of nuclear division leading to cell division in vegetative cells. Meristematic cells (like those found in the shoot tip or root tip) are actively involved in cell division. Root meristem Back to main anatomy menu Next Back to cell biology menu Main menu Cell biology Mitosis – Plane of division Cells division occurs in either an anticlinal or periclinal orientation. Anticlinal is the plane of division perpendicular to the surface of the organ. This is in contrast to periclinal cell divisions that are generally parallel to the outer surface. Anticlinal cell divisions in the epidermis. Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis - Cell cycle The vegetative cell division cycle is divided into two phases. Interphase and Mitosis However, many cells in the plant are not actively dividing and are arrested in interphase. Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis - Cell cycle Interphase is represented as the : G1 Phase S Phase G2 Phase Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis - Cell cycle G1 is the usual resting state for most cells. "G" stands for gap. Once the cell passes the start point it is committed to cell division. Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis - Cell cycle During the S phase both DNA and DNA-related proteins are made. This is the phase where a duplicate copy of the cell's DNA is made. "S" represents synthesis. Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis During interphase, the chromosomes in the nucleus are duplicated. Sister chromatids These chromosome parts both remain in close association. At this time, the chromosome consists of two chromatids held together at the centromere. Back to main anatomy menu Back Centromere Next Back to cell biology menu Main menu Cell biology Mitosis - Cell cycle During the G2 phase the cell prepares to divide. Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis - Cell cycle Mitosis is the phase where the cell actually divides. There are four phases : Prophase Metaphase Anaphase Telophase Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis Prophase During prophase, the chromosomes condense to become well defined. During late prophase, the nuclear envelope's outer membrane dissolves. Nucleus Nucleolus Chromosome Centromere Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis Metaphase During metaphase, the spindle appears and the chromosomes migrate to the center of the former nucleus. Spindle Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis Anaphase Spindle fibers become attached to specialized proteins on the centromeres of each sister chromatid. The spindles contract to pull the sister chromatids to opposite sides of the cell. Each is now considered a daughter chromosome. Spindle fibers Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis Telophase During telophase, the chromosomes migrate to their separate cells and the cell plate begins to form. Cell plate Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis Telophase Finally, the cells separate into duplicate daughter cells. New cell wall Back to main anatomy menu Back Next Back to cell biology menu Main menu Cell biology Mitosis Prophase Back to main anatomy menu Metaphase Back Anaphase Telophase Back to cell biology menu Main menu