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Chapter 9

Chapter 9. MITOSIS (CELL DIVISION) AND CELL CYCLE. Activator— kwl chart mitosis. activator. Name the stages of mitosis in order. Impacts, Issues: Henrietta’s Immortal Cells. Cancer cells isolated from Henrietta Lacks established a self-perpetuating lineage of cancer cells

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Chapter 9

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  1. Chapter 9 MITOSIS (CELL DIVISION) AND CELL CYCLE

  2. Activator—kwl chart mitosis

  3. activator Name the stages of mitosis in order.

  4. Impacts, Issues: Henrietta’s Immortal Cells • Cancer cells isolated from Henrietta Lacks established a self-perpetuating lineage of cancer cells • The cell lineage, name HeLa cells, is used in research laboratories across the world • Henrietta Lacks’ contribution is used to research cancer, viral growth, protein synthesis, effects of radiation, and more

  5. Henrietta’s Immortal Cells Fig. 9-2, p.141

  6. Understanding Cell Division • “Omnis cellula e cellula”---ALL cells from cells • What instructions are necessary for inheritance? • How are those instructions duplicated for distribution into daughter cells? • By what mechanisms are instructions parceled out to daughter cells?

  7. Reproduction • Parents produce a new generation of cells or multicelled individuals like themselves • Parents must provide daughter cells with hereditary instructions, encoded in DNA, and enough metabolic machinery to start up their own operation

  8. Division Mechanisms Eukaryotic organisms • Mitosis(nuclear division) & cytokinesis (cytoplasm division) • Meiosis—ch 10 Prokaryotic organisms • Prokaryotic fission—replicates only a small, single, circular chromosome

  9. HUMAN LIFE CYCLE

  10. Bozeman Video--Mitosis http://www.youtube.com/watch?v=1cVZBV9tD-A

  11. Roles of Mitosis • Multicelled organisms • Growth • Cell replacement • Some protistans, fungi, plants, animals • Asexual reproduction

  12. Cell Division • Individual cells of a human embryo divide, developing from a paddlelike structure into a hand

  13. Cell Division Fig. 9-10, p.149

  14. Chromosome • A DNA molecule & attached proteins • Duplicated in preparation for mitosis onechromosome (unduplicated) one chromosome (duplicated)

  15. Chromosome a One chromosome (unduplicated) onechromatid two sister chromatids onechromatid b One chromosome (duplicated) Stepped Art Fig. 9-3a, p.142

  16. Structure of chromosome pair • Sister chromatids • Centromere • locus

  17. Organization of Chromosomes DNA one nucleosome DNA and proteins arranged as cylindrical fiber histone

  18. Chromosome Number • Sum total of chromosomes in a cell • Somatic cells • Chromosome number is diploid (2n) • Two of each type of chromosome • Gametes • Chromosome number is haploid (n) • One of each chromosome type

  19. The Cell Cycle—alternates between m (mitosis) phase and interphase interphase G1 S telophase anaphase Mitosis G2 metaphase prophase Figure 9.5Page 144

  20. Interphase • Usually longest part of the cycle • Nondividing phase • Cell increases in mass (grows & PREPARES for division) • Number of cytoplasmic components doubles • DNA is duplicated

  21. G1—1st growth phase • S– synthesis (DNA replicates) • G2– 2nd growth phase; considered by some to be the first phase of mitosis

  22. Mitosis • Period of nuclear division • Usually followed by cytoplasmicdivision(cytokinesis) • Four stages: Prophase Metaphase Anaphase Telophase

  23. Control of the Cycle • Once S begins, the cycle automatically runs through G2 and mitosis • The cycle has a built-in molecular brake in G1 • Cancer involves a loss of control over the cycle, malfunction of the “brakes”

  24. Stopping the Cycle • Some cells normally stop in interphase • Neurons in human brain • Arrested cells do not divide • Adverse conditions can stop cycle • Nutrient-deprived amoebas get stuck in interphase

  25. The Spindle Apparatus • Consists of two distinct sets of microtubules • Each set extends from one of the cell poles • Two sets overlap at spindle equator • Moves chromosomes during mitosis

  26. Spindle Apparatus one spindle pole one of the condensed chromosomes spindle equator microtubules organized as a spindle apparatus one spindle pole

  27. chromosome (unduplicated) in cell at interphase same chromosome (duplicated) in interphase prior to mitosis mitosis, cytoplasmic division chromosome (unduplicated) in daughter cell at interphase chromosome (unduplicated) in daughter cell at interphase Maintaining Chromosome Number

  28. Maintaining Chromosome Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 XX (or XY) Fig. 9-6a, p.145

  29. Maintaining Chromosome Number b The same two hromosomes, now duplicated, in that cell at interphase, prior to mitosis c a Two of the chromosomes (unduplicated) in a parent cell at interphase c Two chromosomes (unduplicated) in the parent cell’s daughter cells, which both start life in interphase Fig. 9-6b, p.145

  30. pole Maintaining Chromosome Number pole microtubule of bipolar spindle p.145

  31. Stages of Mitosis Prophase Metaphase Anaphase Telophase

  32. Early Prophase - Mitosis Begins Duplicated chromosomes begin to condenseand become observable under a microscope; mitotic spindle forms Figure 9.7 Page 146

  33. Late Prophase—AKA Prometaphase • New microtubules are assembled • One centriole pair is moved toward opposite pole of spindle • Nuclear envelope starts to break up Figure 9.7 Page 146

  34. Transition to Metaphase • Spindle forms • Spindle microtubules become attached to the two sister chromatids of each chromosome Figure 9.7 Page 146

  35. Metaphase • All chromosomes are lined up at the spindle equator • Chromosomes are maximally condensed Figure 9.7 Page 147

  36. Anaphase • Characterized by MOVEMENT! • Sister chromatids of each chromosome are pulled apart thus elongating the cell • Once separated, each chromatid is a chromosome • Kinetechore vs. nonkinetechoremicrotubles Figure 9.7 Page 147

  37. Telophase • Chromosomes loosen and become less distinct • Two nuclear membranes form, one around each set of unduplicated chromosomes • Cytokinesis starts to produce 2 identical daughter cells • Plasmodia—when some slime molds have NO cytokinesis resulting in mulitnucleated masses Figure 9.7 Page 147

  38. Results of Mitosis • Two daughter nuclei • Each with same chromosome number as parent cell • Chromosomes in unduplicated form Figure 9.7 Page 147

  39. a Cell at Interphase The cell duplicates its DNA, prepares for nuclear division Mitosis pair of centrioles nuclear envelop chromosomes b EARLY PROPHASE c LATE PROPHASE d TRANSITION TO METAPASE Mitosis begins. The DNA and its associated proteins have started to condense. The two chromosomes color-coded purple were inherited from the female parent. The other two (blue) are their counterparts., inherited from the male parent. Chromosomes continue to condense. New microtubules become assembled. They move one of the two pairs of centrioles to the opposite end of the cell. The nuclear envelope starts to break up. Now microtubules penentrate the nuclear region. Collectively, they form a bipolar spindle apparatus. Many of the spindle microtubules become attatched to the two sister chromatids of each chromosome. Fig. 9-7a, p.146

  40. microtubule e METAPHASE f ANAPHASE g TELOPHASE h INTERPHASE All chromosomes have become lined up at the spindle equator. At this stage of mitosis (and of the cell cycle), they are most tightly condensed Attachments between the two sister chromatids of each chromosome break. The two are separate chromosomes, which microtubules move to opposite spindle pores. There are two clusters of chromosomes, which decondense. Patches of new membrane fuse to form a new nuclear envelope. Mitosis is completed. Now there are two daughter cells. Each is diploid; its nucleus has two of each type of chromosome, just like the parent cell. Fig. 9-7b, p.146

  41. Animal Cell Division—cleavage furrow forms at old metaphase plate by way of an actin contractile ring

  42. Animal Cell Division— 1 Mitosis is over, and the spindle is now disassembling. 2 At the former spindle equator, a ring of micro-filaments attached to the plasma membrane contracts. 3As its diameter shrinks, it pulls the cell surface inward. 4Contractions continue; the cell is pinched in two. Fig. 9-8a, p.148

  43. Cell Plate Formation cell plane forming 1As mitosis ends, vesicles cluster at the spindle equator. They contain materials for anew primary cell wall. 2Vesicle membranes fuse. The wall material is sandwiched between two new membranes that lengthen along the plane of a newly forming cell plate. 3 Cellulose is deposited inside the sandwich. In time, these deposits will form two cell walls. Others will form the middle lamella between the walls and cement them together. 4A cell plate grows at its margins until it fuses with the parent cell plasma membrane. The primary wall of growing plant cells is still thin. New material—cellulose- is deposited on it. Fig. 9-8b, p.148

  44. Mitotic Control • Growth factors—such as needed nutrients • Density-dependent inhibition—overcrowding=less growth • Checkpoint(restriction point)—Ex: cells have a checkpoint in G1 where cell can either go on with cycle or go into G 0 (this is where mature muscle and nerve cells are)

  45. CONTINUED MITOTIC CONTROL • CYCLIN-DEPENDENT KINASES-AKA Cdks • enzymes(proteins) which are affected by the cell cycle regulatory protein cyclin; when these enzymes are active & attached to cyclin, then mitosis can happen) • Ex: MPF (maturation promoting factor)

  46. CELL CYCLE & RELATIVE CYCLIN CONCENTRATION

  47. Tumors • Sometimes a checkpoint gene mutates and control over cell division is lost. • Cells uncontrollable division forms an abnormal mass called a tumor. • Neoplasms

  48. Cancer Fig. 9-12, p.150

  49. MALIGNANT VS. BENIGN (see p. 151)

  50. cell at interphase nucleus cytoplasm telophase prophase metaphase anaphase Fig. 9-15, p.153

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