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1. DNA overload 2. Surface area to volume ratio 1. DNA Overload › Size of the cell would be too large for the DNA to control and handle Compare to a small vs. large town. If town gets too big, it can’t supply people with enough resources, like the DNA cant supply the cell 2. Surface area to volume ratio › As cell grows, it needs more resources but surface area can’t bring enough in Volume increases but surface area stays the same Cell Division 2 Major Phases 1. Interphase ›G1 ›S ›G2 2. “M” Phase-Mitosis ›Prophase 1 ›Metaphase ›Anaphase ›Telophase 2 ›Cytokinesis Longest? Shortest? › Interphase › Mitosis › Because it › Because its simply developing all organelles for cell to divide and growing in size reorganizing cell components thought 5 steps and splitting in two Structure of a Chromosome- two “sister” chromatids attached in the middle with a centromere “sister” means they are identical to one another A B C Chromosome a. G1 phase• • most of cell growth is done here. It’s the longest phase make organelles…think 1st growth phase b. S phase• the copying of DNA c. G2 phases• Many organelles required for division are produced like centrioles. Nucleus CELL MEMBRANE Cytoplasm Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm 1. Chromatin becomes shorter and fatter to form chromosomes 2. Centrioles(organelles)appear and move to opposite ends of cell- they work to pull apart chromosomes 3. Spindles form 4. Nucleus starts to break down ** longest phase in Mitosis** Centrioles Sister chromatids Spindle fibers Animal Cell Plant Cell Spindle fibers Centrioles Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Chromosomes attach to spindle and spindle pulls chromosomes to middle of cell Centrioles Spindle fibers Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm Spindle pulls apart chromosome into 2 chromatids that move them to opposite sides of cell ** shortest phase in mitosis** Centrioles Spindle fibers Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm 1. 2. 3. 4. Chromosomes become long and stringy to form chromatin again Centrioles move back together and disappear Spindles break apart Nucleus reforms Nuclei Chromatin Nuclei Animal Cell Plant Cell Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm • Actually splitting of cell into 2 identical daughter cells • Cell membrane moves inward to create two daughter cells. Happens at end of telophase Animal Mitosis -- Review 1. Interphase 2. Prophase 3. Metaphase 4. Anaphase 5. Telophase 6. Cytokinesis Plant Mitosis -- Review 1. Interphase 2. Prophase 3. Metaphase 4. Anaphase 5. Telophase 6. Cytokinesis 25 http://www.cellsalive.com/mitosis.htm