Download Why Do Cells Divide?

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
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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
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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
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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)
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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
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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
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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
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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
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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
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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
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