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Cell division

Cell division. Cells are constantly dividing For growth and for maintenance We need cells to divide, but must maintain careful control Cancer. Telomeres. One control we have is telomeres Long cap at the end of both ends of every chromosome Each cell division shortens it a little

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Cell division

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  1. Cell division • Cells are constantly dividing • For growth and for maintenance • We need cells to divide, but must maintain careful control • Cancer

  2. Telomeres • One control we have is telomeres • Long cap at the end of both ends of every chromosome • Each cell division shortens it a little • Eventually shortens the chromosome itself

  3. Division starts with the DNA • DNA is organized into chromosomes • Prokaryotes: • Single circular chromosome (no telomeres) • Plus plasmids • Eukaryotes: • Multiple linear chromosomes • In nucleus • Wrapped around histone proteins

  4. How cells divide • Prokaryotes: Binary Fission • Duplicate DNA • Elongate • Pinch off • E. coli can do this in 20 minutes

  5. How cells divide • Eukaryotes: more complicated • Division happens in several phases or steps • Governed by the cell cycle • Two types • Mitosis: somatic cells • Meiosis: germ line/reproductive cells

  6. The Cell Cycle • A carefully regulated and orderly process • G1 – normal operations and growth • DNA synthesis – chromosomes replicated • G2 – growth and prep for division • Mitosis – division of genetic material • Cytokinesis – cells physically divide

  7. DNA duplication • Similar to making mRNA transcripts • Unwind the double-helix • Make a copy of each strand • Errors can enter the genetic code – replication errors • http://www.youtube.com/watch?v=4jtmOZaIvS0

  8. Mitosis • Growth and replacement • Constant maintenance as cells wear out and die • Creates two identical daughter cells from a mother cell • PMAT

  9. Chromosomes • Each mitotic chromosome has • Two sister chromatids • Each is a double strand of DNA

  10. Prophase • Nuclear membrane breaks down • Sister chromatids condense • Spindle forms • Part of the cytoskeleton • Fibers extend out from each pole of the cell • Organizes the rest of Mitosis

  11. Metaphase • Sister chromatids line up on the metaphase plate • Center of the cell • Held in place by the spindle

  12. Anaphase • Sister chromatids separate • Pull themselves along the spindle • To opposite poles

  13. Telophase • Chromosomes uncoil • Two nuclear membranes form

  14. Cytokinesis • Cell divides • Closes plasma membrane in between two nuclei • Does this differently in plant and animal cells

  15. Cancer • Unrestrained cell division and growth • Your cells regulate their division carefully • Cancer: • Overcomes contact inhibition • Overcomes telomere shortening • Overcomes health assessment checkpoint in cell cycle

  16. Next time • pp. 225 - 243

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