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Week 9 theory lesson 1 A pril 2014

Week 9 theory lesson 1 A pril 2014. Cell division. The beginning of life. Multi cellular organisms begin as just one cell, which keeps dividing until the organism grows into an adult Cells are also replaced as part of body maintenance ( eg skin/red blood cells). Cell division.

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Week 9 theory lesson 1 A pril 2014

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  1. Week 9 theory lesson1 April 2014 Cell division

  2. The beginning of life • Multi cellular organisms begin as just one cell, which keeps dividing until the organism grows into an adult • Cells are also replaced as part of body maintenance (eg skin/red blood cells)

  3. Cell division • Mitosis- cells divide to produce an identical cell with same DNA • Meiosis- cells divide to produce gametes (sex cells) with ½ the DNA of parent cell

  4. Sites of mitosis • Any area where rapid growth occurs or repair is needed (eg skin/wounds) • Somatic (body) cells originate from pre existing cells via mitosis • All somatic cells originate from an original stem cell in an organism formed via sexual reproduction

  5. Mitosis in Plants-eg roots tips

  6. Mitosis in animals- eg skin

  7. Process of mitosis • Occurs in stages • Interphase • Prophase • Metaphase • Anaphase • Telophase

  8. Interphase • Chromosomes are replicated • Chromosomes double (eg humans have 46  92 are made) • Organelles replicate, centrioles start to separate

  9. Prophase • Chromosomes become visible • Chromosomes held together in pairs (by centromere) • Centrioles move to poles and spindle fibres form • Nuclear membrane breaks down

  10. Metaphase • Chromosomes move through the cytoplasm to the spindle • The centromere attaches to spindle and takes chromosomes to middle of the cell

  11. Anaphase • Centromeres divide (chromosome pairs split) • Chromosomes move to opposite poles of cell along spindle • Cell starts to shrink in the middle

  12. Telophase • Nuclear membranes form around chromosomes • Chromosomes uncoil • Cytoplasm divides to form two cells

  13. Slide of a root tip

  14. Mitosis summary • Mitosis refers to the changes involved in the chromosomes during cell division • Cytokinesis is the division of the cytoplasm and replication of organelles within the cytoplasm • Mitosis is involved in cell division where cells are replicated as part of growth and development

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