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Where we have been.

Where we have been. Cells Organelles Nucleus DNA Replication Chromosomes. Let’s Review. Reproduction – 2 types Asexual Offspring genetically identical to the ONE parent Quick, many offspring Sexual Offspring share genetic information from BOTH parents Creates variation. Curious?.

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Where we have been.

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  1. Where we have been. • Cells • Organelles • Nucleus • DNA • Replication • Chromosomes

  2. Let’s Review • Reproduction – 2 types • Asexual • Offspring genetically identical to the ONE parent • Quick, many offspring • Sexual • Offspring share genetic information from BOTH parents • Creates variation

  3. Curious? • Asexual reproducers • Archea • Bacteria • Protists • Starfish • Sexual reproducers (pregnancy length) • Birds • Humans (9 months) • Insects • Rabbit (33 Days) • Alpine Salamander (38 months) • Elephant (22 months)

  4. Chromosomes • Chromosomes • DNA condensed, wrapped around proteins, called histones • Nucleus • Only visible during cell division • Each organism has its own number • Corn – 20, fruit fly 8, horsetail – 216, Chimp – 48, Dog – 78, humans? Somatic cells? Sex Cells?

  5. Chromosomes • Sister Chromatids • The 2 halves of a replicated chromosome • Centromere • The place where sister chromatids are connected

  6. Cell Division

  7. Cell Division • Why? • Replace lost cells • Repair • Growth and development • Reproduction

  8. Cell Cycle • “ALL CELLS COME FROM CELLS” • The “life cycle” of a cell from the beginning of one division to the beginning of the next division. • The 2 new cells are called Daughter Cells • Cell division • 1 cell becomes 2

  9. The Cell Cycle • Interphase • G1 – primary growth • S – DNA replication • G2 – Cell carries out everyday functions, prepares for division • Mitosis • M – Cell divides • Cytokinesis • Cytoplasm divides

  10. Starter • What is the purpose of cell division? • What are the 3 major steps and what happens in each of the cell cycle? • Why must DNA replication happen before mitosis and cytokinesis? • What are the phases of mitosis? • With a pencil, label your drawings with the stages of the cell cycle, the phases of mitosis and cytokinesis.

  11. Mitosis The Break Down

  12. The Phases • Prophase • Metaphase • Anaphase • Telophase • Cytokinesis

  13. Prophase • The longest phase • Chromatin condenses forming chromosomes (visible) • Centrioles move to opposite sides of the nucleus • Spindle fibers form between them – some of which attach to centromeres on each side of the chromosome • Nuceolus and nuclear membrane disappear

  14. Metaphase • The shortest phase • Chromosomes line up in the center of the cell • Centrioles move to opposite sides of the cell • Spindle fibers are still attached to the centromeres

  15. Anaphase • Centromeres split • Sister chromatids split to make separate chromosomes • Chromosomes move to opposite ends of the cell • This phase ends when the movement stops

  16. Telophase • Chromosomes begin to uncoil back into chromatin • Nuclear membranes develop around the bundles of chromatin at opposite ends of the cell • Spindle fibers disappear • Nucleolus reappear in each new, daughter cell

  17. Cytokinesis • When the cytoplasm divides, cell division is complete.

  18. Not always the same! • Animals • Cell membrane pinches, forming 2 identical daughter cells • Complete cells that are identical • Plants • Cell Plate forms halfway between the 2 nuclei • Materials for new cell walls and membranes gather and fuse in the middle between the 2 nuclei. Material gradually divides to create 2 cells.

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