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The Need for Cell Division

Cell division plays a crucial role in the development of organisms from a single fertilized egg cell to a mature multicellular organism and in repairing damaged or worn out tissues in adults. The process of cell division includes stages like interphase, mitosis, and cytokinesis, ensuring the duplication of key cellular components and genetic information. Understanding the cell cycle phases - G1, S, G2, and mitosis - helps in comprehending how cells grow, replicate DNA, and divide. The intricate process involves various components such as microtubules, chromosomes, and cellular organelles, ultimately leading to the formation of new daughter cells. Through mitosis, the nucleus divides, chromosomes separate, and cytokinesis completes the cell division process. Watch a detailed video explaining the intriguing process of cell division.

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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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