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The Need for Cell Division

The Need for Cell Division. During development One fertilized egg cell begins to divide Develops into a mature multicellular organism In adults To repair damage To replace worn out tissue. Stages of the Cell Cycle. Before a cell can divide: Key cellular components must be duplicated

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The Need for Cell Division

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  1. The Need for Cell Division • During development • One fertilized egg cell begins to divide • Develops into a mature multicellular organism • In adults • To repair damage • To replace worn out tissue

  2. Stages of the Cell Cycle • Before a cell can divide: • Key cellular components must be duplicated • Proteins, membranes, and organelles • Chromosomes must be duplicated • Complete set of genetic information • Ensures that the new cells can survive

  3. The Cell Cycle (eukaryotes): Interphase Mitosis cytokinesis

  4. Interphase has 3 phases: • G1 Phaseor Gap 1: • Longest phase • Cell growth, • Proteins/lipids synthesized, • Prepares for replicating DNA G1 Start after cell division

  5. Interphase: S Phase DNA Synthesis (Chromosomes/chromatin Replicated) S G1

  6. Interphase: G2 Phase • Prepares for cell division, proteins made • Mitochondria replicate • Centrioles replicate • Microtubule synthesis G2 S G1

  7. Mitosis: • Nuclear division • Microtubules separate chromosomes G2 S Mitosis G1

  8. Cytokinesis: • Cell division, divides into 2 daughter cells • Cell may renter cell cycle • Or leave cell cycle (G0) G2 S Mitosis G1 Cytokinesis G0

  9. G0 Phase • Most cells are not actively dividing • These cells are in G0 phase • Can leave cell cycle for days to years • Some cells will divide again; e.g. liver cells • Some cells stay in G0; e.g. nerve cells

  10. Interphase – G1, S, & G2 Phases

  11. MITOTIC PHASES Prophase Metaphase Anaphase Telophase

  12. Mitosis: Prophase

  13. Mitosis: Metaphase • Microtubules grow, connect to centromeres, • and align the chromosomes

  14. Mitosis: Anaphase • Sister chromatids separate, move to opposite poles. • Microtubules shorten & pull them in.

  15. 4 Mitosis: Telophase • Chromosomes at poles • Nucleus reforms • Chromosomes unwind into chromatin • Spindle degrades

  16. Cytokinesis • Cytokinesis follows mitosis. • In animal cells, actin filaments (protein) pinch the cell in two. • Seen as a cleavage furrow on the cell membrane. • Plant cells divide by growing a new cell wall (cell plate) between the 2 nuclei.

  17. DNA Synthesis & Chromosomal Replication: DNA Synthesis Occurs in S-phase of interphase

  18. Chromosomes

  19. Mitosis Review • Allows for: • Growth • Replacement of cells • Asexual Reproduction • Identical Cells • Video of a cell dividing

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