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Cell Division

Cell Division. Multicellular organisms Important in growth and development Single celled organisms Important for reproduction Goals To create 2 identical daughter cells. Genetic Material Equally Distributed. What has to occur in order for genetic material to be equally distributed?

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Cell Division

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  1. Cell Division • Multicellular organisms • Important in growth and development • Single celled organisms • Important for reproduction • Goals • To create 2 identical daughter cells

  2. Genetic Material Equally Distributed • What has to occur in order for genetic material to be equally distributed? • Each new cells contains the total number of chromosomes as the parent cell • DNA has to replicate • Before we talk about replication we need to understand more about DNA

  3. The Structure of DNA • Double Helix • Sugar Phosphate Backbone • Made of nucleotides

  4. p NUCLEOTIDES base base sugar sugar p p base base sugar sugar p Bases Guanine – Cytosine Thymine - Adenine

  5. DNA Replication

  6. Before we go on to cell division: • What is the structure of DNA? • How are the bases paired? • What is the function of DNA? • Replicate the following chain: • TAC TTG AAA TGA CCC ACG ACT • AUG AAC TTT ACT GGG TGC TGA

  7. Back to Cell Division • Cells pass through a life cycle of 5 phases • In single-celled eukaryotes, • cell cycle is the major mechanism for asexual reproduction • In multicellular eukaryotes, • Development • Growth

  8. Cell Cycle Overview • Key Events • Cell grows (interphase) • DNA doubles (interphase) • Nucleus divides (prophasetelophase) • Cyotplasm divides (telophase)

  9. Mitosis an Overview • Interphase each chromosome is uncoiled and in an unreplicated state

  10. Mitosis an Overview • interphase, each chromosome is replicated. The replicated chromosome consists of two sisterchromatids attached at the centromere.

  11. Mitosis an Overview • At the beginning of mitosis, the chromosomes coil and become visible (still Interphase). Note that the chromosome is still in a replicated state, with a sister chromatids attached at the centromere.

  12. Mitosis an Overview • Anaphase: the centromere splits, the sister chromatids separate and become daughter chromosomes, the daughter chromosomes move to opposite sides of the cell.

  13. Mitosis an Overview • At the end of mitosis, the chromosomes on each side of the cell uncoil and form two new, identical nuclei. (telophase)

  14. A.Prophase • 1.Chromosomes coil up and become individually visible. • 2.The nuclear membrane disappears • 3.The mitotic spindle will form between the centrosomes. • 5. microtubules attach to the centromere of each sister chromatid

  15. A.Metaphase • 1.  Chromosomes line up on the middle of the spindle. • 2.  Each chromosome has microtubules attached to the centromere of each of its sister chromatids.

  16. B.     Anaphase • 1.  Chromosomes move to opposite ends of the cell. One chromatid from each chromosome goes to each end of the cell. • Use spindel fibers to do this • a)  Why can’tDNA fragments without a centromere be passed on to further generations? • b) Why can’t chromosomes have more than one centromere?

  17. A.Telophase • 1.Chromosomes reach the opposite ends of the cell. • 2.Chromosomes uncoil • 3.The spindle disintegrates, • 4.The nucleolus reappears • 5.  The cytoplasm divides in a process known as cytokinesis. • a)  using either a cell plate or cleavage furrow • b). This produces two cells each identical to the original cell (except, of course for errors in DNA duplication).

  18. Mitosis an Overview • During what stage of the cell cycle do the drawings take place? • What is a chromosome? A chromatid? A sister chromatid? A daughter chromosome? And in what stage of the cell cycle do we find each?

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