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Mitosis

Mitosis. AP Biology Crosby High School. Cell Division. Reproduction, Growth, and Repair Basic steps: Duplicates DNA Copies split to opposite ends Cell splits 2 Daughter Cells formed. Genome. Prokaryote vs. Eukaryote Prokaryote: Single strand of DNA Eukaryote:

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Mitosis

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  1. Mitosis AP Biology Crosby High School

  2. Cell Division • Reproduction, Growth, and Repair • Basic steps: • Duplicates DNA • Copies split to opposite ends • Cell splits • 2 Daughter Cells formed

  3. Genome • Prokaryote vs. Eukaryote • Prokaryote: Single strand of DNA • Eukaryote: • More than on strand of DNA • Each species has a specific number of chromosomes • Human Somatic Cells: 46 chromosomes (Diploid) • Human Gametic Cells: 23 chromosomes (Haploid)

  4. Structures and Overview of Splitting • DNA strand wrapped around proteins • Chromatin: DNA/Protein complex • Condenses to form Chromosomes • Copied forming Sister Chromatids • Chromatids joined at Centromere • Chromatids separate in Mitosis • Cytoplasm separates in Cytokinesis

  5. Interphase • 90% of Cell Cycle • Consists of Three Phases • G1 Phase (Gap one) • Growth of the cell • S Phase (Synthesis) • Growth of the cell • DNA replication • G2 Phase (Gap two) • Growth of the cell

  6. Mitotic Phase • “Please Pour Me Another Tequila” • Prophase • Prometaphase • Metaphase • Anaphase • Telephase

  7. Mitotic Spindle • Centrosomes form spindles • Centriole pairs inside Centrosomes • Centrosomes replicate near nucleus • Two centrosomes grow spindle microtubules • Separate to opposite ends of the cell • Spindles “play tug-o-war” at Kinetochores • Pull both directions until chromosomes reach metaphase plate

  8. Mitotic Spindles and Anaphase • Proteins holding sister chromatids deactivate • Chromosomes “walk” along microtubules • Microtubules shorten by depolymerizing • Nonkinetochore microtubules lengthen the cell

  9. Cytokinesis • Begins with Cleavage furrow • Actin and Myosin contraction • Differences of Plant Cytokinesis • Vesicles from Golgi form cell plate • Plate grows and fuses with plasma membrane • Cell wall materials accumulate and form cell wall

  10. Mitosis: Evolution of Binary Fission? • Prokaryotes have no spindle fibers • Origin of Replication replicates in opposite directions • Plasma membrane grows inward • Dinoflagellates and Diatoms • Unicellular algae • Divides with nuclear envelope intact

  11. Cell Cycle Regulation • Controlled on the molecular level by signals • Fused cells could force Mitosis • Fused to have two nuclei • Performed same function • Cell cycle control system • Internal signals • External signals

  12. Cell Cycle Checkpoints • 3 major checkpoints • G1(Restriction point) • Begins the S phase • Decides whether the cell will divide or not • Yes: Enters S phase • No: Enters G0 phase • G2 • Precedes mitosis • M • Has mitosis completed?

  13. Cyclin and Cyclin Dependent Kinases • Cyclin • Fluctuates in the cell • When present bind to Cdks for activation • G1 checkpoint contains 3 Cdks and several cyclins • Maturation Promoting Factor (MPF) • Past G2 • Initiates Mitosis by phosphorylating proteins • Turns itself off by degrading cyclin • Remains present in inactive form

  14. Internal Signals • Messages received from Kinetochores • Anaphase does not begin until all kinetochores are attached to a spindle fiber • Signal comes from non-attached • Anaphase promoting complex (APC) inactive • Active: APC triggers breakdown of cyclin and deactivation of sister chromatids

  15. External Signal • Platelet-derived Growth Factor (PDGF) • Fibroblasts have PDGF receptors • Heals wounds • Density dependent Inhibition • Cells form one layer IN CULTURE and stop • Continue to grow when cells are removed • Anchorage Dependence • Must be attached to substratum

  16. Cancer • Uncontrolled cell growth • Control point malfunctions • Cell continues to grow beyond inhibition • HeLa cells have been growing since 1951

  17. Onset of Cancer • Transformation: cell malfunctions • If not destroyed it becomes a tumor • Benign: Remains at origin • Malignant: invasive enough to impair organs • Cells lose function and inhibition • Cells lose attachment and spread • Spread through lymphatic or blood vessels • Metastasis

  18. Cancer

  19. Mitosis

  20. Mitosis (cont.)

  21. Spindle Shortening

  22. Cyclin and MPF

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