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Cellular Reproduction http://www.nature.com/scitable/content /mitosis-6656772 SJCHS Why Must Cells Divide? • If cell is too large, not enough nutrients can get in Why Do Cells Divide? • Reproduction • Growth • Repair/ Maintenance of cells 1 Chromosomes • Chromosomes- Different number for different species • Higher number of chromosomes does not mean a more complex species Binary Fission • Binary Fission: Method of cell division for many prokaryotes • DNA copied • Cell elongates, plasma membrane forms between DNA copies Cell Cycle • Cell Cycle: Cycle of events from creation of eukaryotic cell to division •Interphase: Cell performs normal functions • Mitotic Phase: Nucleus (DNA) divides • Cytokinesis: Cell divides Cell Division • Cell cycle control system: Control system that supervises cell division 2 Cell Division • Cell cycle control system controlled by growth factors (external chemical signals) Cell Division • Cell division occurs if growth factor signals cell to divide Interphase • G1 (“Gap” 1) • New organelles created, cell grows Cell Cycle Check Point • • Determines if cell will divide G0: Permanent phase of cells that don’t divide 3 Interphase • S phase (Synthesis Phase) • DNA duplicated Cell Cycle Check Point • No errors in DNA replication Interphase • G2 • More cell growth, prepare for division Mitotic Phase • M Phase (Mitotic Phase) 4 Mitosis • Centrioles - Organelle produces microtubules • Centrosomes - Clouds of cytoplasmic material, contains centrioles • Spindle: Microtubules that separate chromosomes Mitosis • Mitosis Phase 1: Late Prophase • Nucleus breaks up • Spindles latch onto chromosomes Mitosis • Mitosis Phase 1: Early Prophase • Chromosomes, spindle form • Centrosomes separate Mitosis • Mitosis Phase 2: Metaphase • Chromosomes line up in center of cell 5 Cell Cycle Check Point • Chromosomes are aligned correctly Mitosis • Mitosis Phase 4: Telophase • Nucleus forms around each set of chromosomes • Spindle disappears Mitosis • Mitosis Phase 3: Anaphase • Chromosomes separate, copy pulled to side • Spindles not attached lengthen Cytokinesis • Cytokinesis • Occurs concurrently with telophase • Varies with plants and animals 6 Cytokinesis •Animals • Microfilament ring contracts • Cell is “pinched” apart Cytokinesis •Plants • New cell wall built in middle of cell • http://www.youtube.com/watch?v=0oJ ZDKdperU&feature=related • http://www.youtube.com/watch?feature =endscreen&NR=1&v=moL5C8SjeJU • http://www.youtube.com/watch?v=DD3 IQknCEdc 7 8 Cancer Review • Cell cycle control system: Control system that supervises cell division SJCHS Review • Cell cycle control system controlled by growth factors (external chemical signals) Review • Cell division occurs if growth factor signals cell to divide 9 Cell Division • Cancer: Disease of cell cycle • Cells are immortal, do not perform the correct function, continuously divide, does not go through apoptosis • Caused by multiple DNA mutations http://www.youtube.com/watch?v=PwqY 99gNipE Cancer Cancer • • • Start: One cell transforms to cancer cell Immune system usually destroys abnormal cells Tumor: Abnormally growing mass of body cells • Benign Tumor: Remains at original site • Malignant Tumor: Spreads to neighboring tissue (cancer) • Metastasis: Spread of cancer cells beyond original site 10 Treatment • First: Surgically remove tumor Treatment • Radiation Therapy • Use high energy radiation, damages DNA disrupts cell division • Problems: Can harm healthy cells, nausea, hair loss, sterility Treatment • “Poison”- ChemotherapyAttempt to stop cancer cell from dividing using prescription drugs 11