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The Cell Cycle

The Cell Cycle. Chromosomes. Before a cell can divide into two daughter cells, the chromosomes must replicate themselves A duplicated chromosome is made of DNA, and is in the form of the letter “X”

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The Cell Cycle

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  1. The Cell Cycle

  2. Chromosomes • Before a cell can divide into two daughter cells, the chromosomes must replicate themselves • A duplicated chromosome is made of DNA, and is in the form of the letter “X” • The two halves of the “X” are referred to as sister chromatids, because they are copies of one another

  3. Cell Division • The centromere holds the “X” together

  4. The Cell Cycle • The cell cycle is a series of changes that a cell goes through from the time it is formed until it divides • The cell cycle is broken down into 2 main parts: Interphase and the Mitotic Phase

  5. The Cell Cycle

  6. Interphase • Interphase can be thought of as the “everyday life” of the cell where it performs all of its usual activities • Interphase is broken down into 3 phases; G1, S, and G2 • G1 - Stage of cell growth • S - DNA is copied (chromosome duplication) • G2 - Cell produces more organelles

  7. Mitotic Phase • During the mitotic phase, the cell divides its nucleus and its cytoplasm • Mitosis is the process of the division of the eukaryotic cell nucleus into two identical nuclei • Mitosis occurs in 4 stages A. Prophase B. Metaphase C. Anaphase D. Telophase • Cytokinesis, the division of the cytoplasm and organelles, occurs during and after telophase

  8. Cell Division • Why do cells divide? • Cells divide because they can not get too big (too big = difficult time obtaining enough resources!) • Cells divide so that an organism can grow, reproduce, and repair/replace old or damaged cells

  9. A closer look at Interphase Interphase • Cell grows and prepares for division • DNA has replicated, but has not yet formed into chromosomes

  10. A closer look at the Mitotic Phase Prophase • The DNA shortens and condenses to form chromosomes • The nuclear membrane and nucleolus are no longer visible • The centrioles move to the poles, and spindle fibers begin to form

  11. A closer look at the Mitotic Phase Metaphase • The chromosomes line up along the equatorial line of the cell. • Spindle fibers attach themselves to the centromeres of each chromosome

  12. A closer look at the Mitotic Phase Anaphase • The spindle fibers shorten and the centromere splits • The sister chromatids are pulled apart towards the centrioles

  13. A closer look at the Mitotic Phase Telophase • The chromosomes reach the poles of their respective spindles • Nuclear membranes form • The spindle fibers disintegrate

  14. A closer look at the Mitotic Phase Cytokinesis • Occurs during and after telophase, the cell is pinched in two and cytoplasm evens out so both cells are about equal size

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