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CELL DIVISION

CELL DIVISION. Cell Division. One cell  Two identical cells Cells must be able to pass on ALL information from their DNA So DNA must be replicated before cell division occurs. Prokaryotic Cells. No nucleus DNA is found as circular molecule BINARY FISSION DNA replicates

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CELL DIVISION

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  1. CELL DIVISION

  2. Cell Division • One cell  Two identical cells • Cells must be able to pass on ALL information from their DNA • So DNA must be replicated before cell division occurs

  3. Prokaryotic Cells • No nucleus • DNA is found as circular molecule • BINARY FISSION • DNA replicates • DNA attaches to membrane • Cell pinches & splits

  4. Eukaryotic Cells • Much more complicated • Chromosome – DNA coiled around proteins

  5. Formation of chromosomes • DNA at “rest” found unorganized in nucleus • Just before cell division, it organizes itself into chromosomes

  6. Human Chromosomes

  7. Parts of a Chromosome

  8. UNDERSTANDING CHECK

  9. How many do humans have? • Somatic cells = DIPLOID (2n) • 46 chromosomes (23 pairs) • 22 pairs = Autosomes • 1 pair = Sex chromosomes (X & Y) • XX (female) vs. XY (male)

  10. Human Karyotype

  11. Human Karyotype

  12. UNDERSTANDING CHECK

  13. Gametes = HAPLOID (n) Formed from germ cells 23 chromosomes (one of each) Sperm + Egg = Zygote  YOU! 23 + 23 = 46 How many do humans have?

  14. Haploid + Haploid = Diploid

  15. Cell Cycle

  16. Cell Cycle • G1 – 1st Growth – Routine functions • S – Synthesis – DNA Replication • G2 – 2nd Growth – Prepare to Divide • M – Mitosis – Division of the Nucleus • C – Cytokinesis – Division of the Cytoplasm • MOVIE

  17. UNDERSTANDING CHECK

  18. Cell Cycle • Numerous ways to control speed • Malfunction of cell cycle = cancer

  19. Interphase • Includes the G1, S, & G2 phases • When the cell is not dividing or “at rest” • DNA is found unorganized in the nucleus

  20. Interphase

  21. Mitosis • Division of the nucleus to form 2 identical nuclei • Chromosome = 2 identical chromatids (formed after replication)

  22. UNDERSTANDING CHECK

  23. Mitosis • Prophase • Metaphase • Anaphase • Telophase • MOVIE 1 • MOVIE 2

  24. Prophase • Chromosomes become visible • Nuclear envelope dissolves • Spindle forms from centrioles

  25. Prophase

  26. Metaphase • Chromosomes line up along equator

  27. Anaphase • Chromatids separate and reeled to opposite poles

  28. Telophase • Nuclear envelope forms at each pole • Chromosomes uncoil • Spindle dissolves • Cytokinesis begins

  29. Telophase

  30. UNDERSTANDING CHECK

  31. Cytokinesis • Division of the cytoplasm • Animal cells – pinch and split • Plant cells – forms cell plate down the center • MOVIE

  32. Meiosis • Formation of haploid gametes from one germ cell • Homologous chromosomes – chromosomes of similar size, shape, & genetic content

  33. Meiosis • Meiosis I • Prophase I • Metaphase I • Anaphase I • Telophase I • Meiosis II • Prophase II • Metaphase II • Anaphase II • Telophase II

  34. Prophase I • Homologous chromosomes pair up & crossing over occurs • Animation • Allows genetic variation

  35. Prophase I • Chromosomes become visible • Nuclear env. breaks down • Spindle forms • Crossing over

  36. Metaphase I • Pairs of homologous chromosomes move to equator of cell

  37. Anaphase I • Homologous chromosomes reeled to opposite poles

  38. Telophase I • Chromosomes gather at poles • Cytokinesis

  39. Prophase II • New spindle forms

  40. Metaphase II • Chromosomes line up on equator

  41. Anaphase II • Chromatids reeled to opposite poles

  42. Telophase II • Nuclear envelope forms • Cytokinesis

  43. Meiosis

  44. UNDERSTANDING CHECK

  45. What can go wrong? • Nondisjunction– the chromosomes fail to separate during meiosis • Trisomy – individual has 3 of a particular chromosome • Down syndrome = trisomy 21

  46. UNDERSTANDING CHECK

  47. Meiosis in Males

  48. Meiosis in Females

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