Cell Division PowerPoint

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Cell Division

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Asexual reproduction involves a single parent cell dividing to make 2 new daughter cells that are genetically identical to the parent. Examples: Mitosis & Binary fission Sexual reproduction involves cells from two parents (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells. Example: Meiosis Types of Cell Reproduction

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All cells are derived from pre-existing cells. Cell division differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, and animals). Cell Division

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Prokaryotes reproduce asexually by dividing into 2 identical cells by the process of binary fission . Single chromosome makes a copy of itself. Cell wall forms between the chromosomes dividing the cell. Parent cell 2 identical daughter cells Chromosome replicates Cell splits Cell Division in Prokaryotes

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Prokaryotic Cell Undergoing Binary Fission http://www.youtube.com/watch?v=3cD3U2pgb5w

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Two types of cell division: Mitosis results in new cells that are identical to the original cell. Meiosis occurs during the formation of gametes (haploid reproductive cells). More on this topic later. Cell Division in Eukaryotes

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In eukaryotes, cell division occurs in two major stages. The first stage, division of the cell nucleus , is called mitosis . The second stage, division of the cell cytoplasm , is called cytokinesis . Note: The following process is how all human cells are made except reproductive (sperm and egg) cells! Mitosis and Cytokinesis

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Mitosis follows Interphase, so the DNA is already duplicated . Biologists divide the events of mitosis into four phases: (PMAT) Prophase Metaphase Anaphase Telophase Cell Cycle Mitosis Remember: P itt M ade A nother T ouchdown

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Mitosis

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Prophase Spindle forming Chromosomes (paired chromatids) Centromere Prophase P itt

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Prophase Prophase is the longest phase of mitosis. The centrioles separate and take up positions on opposite sides of the nucleus. Spindle forming Centromere Chromosomes (paired chromatids) P itt

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Prophase The centrioles lie in a region called the centrosome . The centrosome helps to organize the spindle , a fanlike microtubule structure that helps separate the chromosomes. Spindle forming Centromere Chromosomes (paired chromatids) P itt Centriole

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Prophase Chromatin condenses into chromosomes. The centrioles separate and a spindle begins to form. The nuclear membrane breaks down. Spindle forming Centromere Chromosomes (paired chromatids) P itt Centriole

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Centriole Centriole Spindle Metaphase Metaphase M ade

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Metaphase The chromosomes line up across the center of the cell. Spindle fibers attach to the centromere of each chromosome. Centriole Spindle M ade

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Individual chromosomes Anaphase Anaphase A nother

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Anaphase The sister chromatids separate into individual chromosomes. The chromosomes continue to move until they have separated into two groups at opposite ends of the cell. Individual chromosomes A nother

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Nuclear envelope reforming Telophase Telophase T ouchdown

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Telophase Chromosomes gather at opposite ends of the cell and lose their distinct shape. Spindle fibers disassemble . New nuclear membranes form around each cluster of chromosomes. T ouchdown Cleavage furrow in animal cell

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Cytokinesis Cytokinesis

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During cytokinesis, the cytoplasm pinches in half . Each daughter cell has an identical set of duplicate chromosomes. Each daughter cell is smaller than parent cell and must grow in size to become mature cells during G 1 of Interphase . Cytokinesis

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In plant cells , a structure known as the cell plate forms midway between the divided nuclei. In animal cells , a structure called cleavage furrow forms. Cell wall Cell plate Cleavage Furrow in Animal Cell Cell Plate in Plant Cell Cytokinesis: Animals vs. Plants

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Interphase Anaphase Telophase & Cytokinesis Metaphase Mitotic spindle Prophase Nucleus with un-condensed chromosomes Equator of the cell Condensed chromosomes Disappearing nuclear membrane Poles of the cell Mother cell Two daughter cells Remember: P itt M ade A nother T ouchdown http://www.youtube.com/watch?v=VlN7K1-9QB0&feature=related http://highered.mcgraw-hill.com/sites/dl/free/0078617022/164155/00053413.html http://www.youtube.com/watch?v=Q6ucKWIIFmg Stages Of Mitosis

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Visual Concept Comparison of Cell Division in Prokaryotes and Eukaryotes

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A cell spends most of its time in interphase . What tells the cells to exit interphase and begin dividing? The cell cycle is regulated by proteins . Proteins regulate the cell cycle by allowing the cell cycle to proceed only when certain processes have happened inside the cell. Proteins also respond to events outside the cell and direct cells to speed up or slow down the cell cycle. There are three main checkpoints that act as “traffic signals” for the cell to divide or not to divide. Control of Cell Division

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Cell growth (G 1 ) checkpoint – controls whether the cell will divide DNA synthesis (G 2 ) checkpoint – makes sure DNA was copied properly Mitosis checkpoint – signals tell the cell to exit mitosis Control of Cell Division http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__control_of_the_cell_cycle.html

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Certain genes contain the information necessary to make the proteins that regulate cell growth and division. If one of these genes is mutated , the protein may not function, and regulation of cell growth and division can be disrupted . Cancer, the uncontrolled growth of cells , may result. Although mutations can occur spontaneously, many occur as a result of environmental influences . Examples : tobacco products, exposure to ultraviolet radiation, certain viruses If mitosis is not controlled, unlimited cell division occurs causing cancerous tumors. Cancer cells may break loose from tumors and spread throughout the body, disrupting normal activities and causing serious medical problems or even death. http://www.youtube.com/watch?v=TpALjMJEb50 Cancer Cells When Control Is Lost: Cancer