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GENETICS Mitosis and the Cell Cycle Cell reproduction How do little elephants grow up to be BIG elephants? Why do animals shed their skin? Three reasons why cells reproduce by asexual reproduction: 1. Growth 2. Repair 3. Replacement Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun. Animated Mitosis Cycle http://www.cellsalive.com/mitosis.htm As you can see Mitosis is a continuous cycle and does not stop at each phase like shown in the picture. The Cell Cycle The sequence of growth and division of a cell. 95% of cell cycle in interphase 5% of cell cycle in mitosis Interphase Stage 1 (G1) – metabolic activity of the cell Synthesis Stage (S) – metabolic activity of the cell, replication of DNA Growth Stage 2 (G2) – metabolic activity of the cell, prepare for division Growth Interphase Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm MITOSIS There are four phases of mitosis. PROPHASE METAPHASE ANAPHASE TELOPHASE Prophase Nuclear membrane fades Chromosomes condense – can see sister chromatids and centromere Spindle forms Centrioles start to move to opposite poles Prophase Animal Cell Plant Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Metaphase Chromosomes line up along the equator (middle) of the cell Each chromatid is attached to spindle with centromere Metaphase Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Plant Cell Anaphase Centromeres divide Sister chromatids are pulled apart to opposite poles of the cell Each chromatid is now a separate chromosome Anaphase Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Plant Cell Telophase Spindle fibers dissolve Chromosomes reach the opposite poles and begin to uncoil (lengthen) Nuclear envelopes (2) reform Telophase Animal Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Plant Cell Cytokinesis Cytoplasm divides Two new daughter cells are now separate Animal Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase Plant Mitosis -- Review Interphase Prophase Metaphase Anaphase Telophase Interphase