Bio Ch10 Cell Division

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  1. Chromosomes:
    • in nuclei of eukaryotes
    • in most animal cells as pairs
    • pairs are called -diploids

    • Example: humans have 46 chromosomes (23 pairs)
    • Every species has diff. # of chromosomes
  2. Chromsomes structure
    made of chromatin (40%DNA 60%PROTEIN)

    • Dna has to coil up to fit
    • During cell divison all dna is coiled up (condensed)
    • Rest of time- DNA is uncondensed (its being used)
  3. Euchromatin:
    DNA uncondensed- being used
  4. Heterochromatin:
    DNA stays condensed all the time
  5. Diploid:
    pair of cells
  6. Homologous pair:
    • Cohesion- helps hold together
  7. Haploid:
    1 copy of eacch chromosome (sex cells)
  8. Karyotype:
    • overall appearancee/array of chromosomes in a cell
    • -used to diagnose some defects
  9. Cell Cycle "process of growth and divison"
    • 1) G1: gap phase 1 long, lots of growth
    • 2) S: DNA synthasized
    • 3) G2: gap phase 2, more synthesize
    • 4) Mitosis - division of 1 nucleus into 2 nuclei (not cell division)
    • 5)Cytokinesis - Division of 1 cell into 2 cells
  10. Mitosis:
    • 1879 Flemming:
    • working w salamander larvae he described mitosis

    • Phases:
    • Prophase: chromsomes condense, become visible, nuclear membrane disapears, everything organized

    Metaphase: lined up on equator of cell(microtubules attached)

    Anaphase: Seperation of chromatids -->become chromosomes

    Telophase: finale destination--> 2 nuclei
  11. Diploid/Haploid mitosis:
    • Diploid has 2 copies (2N cell)
    • Haploid has 2 copy (1N cell)

    if diploid cell undergoes mitosis it produces 2-2N cells (identical)
  12. Cytokenesis:
    • 2 cells from 1 cell (divison of 2 cells)
    • Plant cells:

  13. Cell cycle control:
    • 3 checkpoints:
    • 1) G1/S checkpoint - is cell big enought to divide?

    • 2) G2/M checkpoint - is dna ok? Gene called P53 checks on DNA. If there is a problem - a)repair b) apoptosis-cell suicide

    3) Spindle checkpoint - is spindle properly attached? Are chromosome attached properly to spindle?
  14. Control of the cell cycle at molecular level:
    • 2 kinds of proteins:
    • 1) Cdks - cyclin-dependent kinase (activation molecule)
    • 2) cyclins - attach to Cdk

    Cdks: measured (cell size/DNA ratio) = when this ratio is big enojugh it will divide.
  15. Control of cell cycle at multicellular level:
    • Sense density of neighboring cells signals:
    • a) inhibitory signals - slow things down
    • b) growth factors (signals that have receptors & small amounts) - PDGF "Platelet Divide Growth Factor"
    • plateletes involved in clotting blood... need to heal wound--> platelets produce PDGF to send signal to nearby cells (fibroblasts) to heal wound.

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Bio Ch10 Cell Division
2012-02-27 01:13:14

Cell Division
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