A.P. Biology Chapter 12: The Cell Cycle

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  1. the ability of organisms to provide more of their own kind best distinguishes living things from nonliving matter
  2. the continuity of life is based on the reproduction of cells or cell division
  3. in unicellular organisms, division of one cell reproduces the entire organism
  4. multicellular organisms depend on cell division for:
    • development
    • growth
    • repair
  5. cell division is an integral part of the cell cycle, the life of a cell from formation to its own division
  6. most cell division results in daughter cells with identical genetic information (DNA)
    -the exception is meiosis, a special type of division that can produce sperm and egg cells
  7. all the DNA in a cell constitutes the cells genome
    -a genome can consist of a single DNA molecule (common in prokaryotic cells) or a number of DNA molecules (common in eukaryotic cells)
  8. DNA molecules in a cell are packaged into chromosomes
  9. eukaryotic chromosomes consist of chromatin, a complex of DNA and protein that condenses during cell division
    -every eukaryotic species has a characteristic number of chromosomes in each cell nucleus
  10. somatic cells:
    (nonreproductive cells) have 2 sets of chromosomes
  11. gametes:
    (reproductive cells) have half as many chromosomes as somatic cells
  12. in preparation for cell division, DNA is replicated and the chromosomes condense
  13. each duplicated chromosome has 2 sister chromatids (joined copies of the original chromosome) which separates during cell division
  14. centromere:
    the narrow "waist" of the duplicated chromosome, where the 2 chromatids are most closely attached
  15. during cell division, the 2 sister chromotids of each duplicated chromosome separate and move into 2 nuclei
    -once separated, the chromatids are called chromosomes
  16. eukaryotic cell division consists of:
    • mitosis (the division of the genetic material in the nucleus)
    • cytokinesis (the division of the cytoplasm)
  17. meiosis yields nonidentical daughter cells that have only one set of chromosomes, half as many as the parent cell
  18. the cell cycle consists of:
    • mitotic (M) phase (mitosis and cytokinesis)
    • Interphase (cell growth and copying of chromosomes in preparation for cell division), can be divided into subphases (G1 phase: "first gap"; S Phase: "synthesis"; G2 Phase: "second gap"
  19. mitosis is divided into 5 phases:
    • 1. prophase
    • 2. prometaphase
    • 3. metaphase
    • 4. anaphase
    • 5. telophase
  20. mitotic spindle:
    a structure made of microtubules that controls chromosome movement during mitosis
  21. in animal cells, assembly of spindle microtubules begins in the centrosome
    -the centrosome replicates during interphase, forming 2 centrosomes  that migrate to opposite ends of the cell during prophase and prometaphase
  22. an aster (a radial array of short microtubules) extends from each centrosome
  23. during prometaphase, :
    some spindle microtubules attach to the kinetochores of chromosomes and begins to move the chromosomes
  24. kinetochores:
    protein complexes associated with centromeres
  25. at metaphase, :
    • the chromosomes are all lined up at the metaphase plate (an imaginary
    • structure at the midway point between the spindles' 2 poles)
  26. in anaphase, :
    • sister chromatids separate and move along the kinetochore microtubules toward opposite ends of the cell
    • -the microtubules shorten by deploymerizing at their kinetochore ends
    • -nonkinetochore microtubules from opposite poles overlap and push against each other, elongating the cell
  27. in telophase, :
    genetically identical daughter nuclei form at opposite ends of the cell
  28. cytokinesis begins during anaphase or telophase and the spindle eventually disassembles
  29. cleavage:
    in animal cells, cytokinesis occurs by the process called cleavage, forming a cleavage furrow
  30. in plant cells, a ________ forms during cytokinesis
    cell plate
  31. prokayotes (Bacteria & Archaea) reproduce by a type of cell division called __________
    binary fission
  32. in binary fission, :
    • the chromosome replicates (beginning at the origin of replication) and the 2 daughter chromosomes actively move apart
    • -the plasma membrane pinches inward, dividing the cell into 2
  33. since prokaryotics evolved before eukaryotes, mitosis probably evolved from binary fission
  34. the cell cycle appears to be driven by specific chemical signals present in the ______
  35. the sequential events of the cell cycle are directed by a distinct cell cycle control system, which is similar to:
    a clock
  36. the cell cycle control system is regulated by:
    internal & external controls
  37. the clock has specific checkpoints where, :
    the cells cycle stops until a go-ahead signal is received
  38. if the cell receives a go-ahead signal at the G1 checkpoint it will usually complete:
    the S, G2, and M phases and divide
  39. if the cell doesn't receive the go-ahead at G1 checkpoint, it will:
    exit the cycle, switching into a nondividing state called G0 phase
  40. 2 types of regulatory proteins involved in cell cycle control:
    • 1. cyclins
    • 2. cyclin-dependent kinases (Cdks)
  41. Cdks activity fluctuates during the cell cycle because it is controlled by cyclins
  42. MPF (maturation-promoting factor):
    a cyclin-Cdk complex that triggers a cell's passage past the G2 checkpoint into the M phase
  43. an example of an internal sign is:
    kinetochores not attached to spindle microtubules send a molecular signal that delays anaphase
  44. some external signals:
    • 1. growth factors (proteins released by certain cells that stimulate other cells to divide)
    • 2. density-dependent inhibition (crowded cells stop dividing)
    • 3. most animal cells exhibit anchorage dependence (they must be attached to a substratum in order to divide)
  45. -cancer cells don't respond normally to the body's control mechanisms
    -cancer cells may not need growth factors to grow and divide, they may:
    • make their own growth factor
    • convey a growth factor's signal without the presence of the growth factor
    • have an abnormal cell cycle control system
  46. transformation:
    the process by which a normal cell is converted to a cancerous cell
  47. cancer cells not eliminated by the immune system form tumors (_________)
    masses of abnormal cells within otherwise normal tissue
  48. benign tumor:
    the lump of abnormal cells that remain at the original site
  49. malignant tumors:
    invade surrounding tissues & can metastasize, exporting cancer cells to other parts of the body, where they may form additional tumors
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A.P. Biology Chapter 12: The Cell Cycle
2014-11-12 02:31:04

notes for ch. 12
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