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4. cell division


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4. cell division

  1. 1. I. GENERALA. REVIEW DNA 1. NUCLEOTIDE 2. DOUBLE HELIX – two nucleotide chains C-G A-T
  3. 3. 2. DEFINITIONS a. DNA – A double helix molecule polymer with genetic information. b. GENE – A segment of DNA that codes for a specific trait. c. CHROMATIN – Uncondensed structures made of DNA & proteins found in the nucleus with genes on it.
  4. 4. d. CHROMOSOME – A condensed structure of DNA & proteins found in the nucleus with genes on it. Gene 1 Gene 2 Gene 31 chromosome 1 chromosome1 chromatid = a single DNA molec. 2 chromatids = two DNA molec.
  5. 5. e. DIPLOID – An individual (cell, etc.) has 1 pair of chromosomes with the same genes. The chromosomes can have 1 or 2 chromatids each. orf. HAPLOID – An individual (cell, etc.) has 1 chromosome with specific genes. The chromosome can have 1 or 2 chromatids each. or
  6. 6. g. HOMOLOGOUS PAIR – two chromosomes in a single cell that have the same genes. Found in diploid organisms. Homologous pair where the Homologous pair where the chromosomes of the pair have only chromosomes of the pair have one chromatid. two chromatids.
  8. 8. C. EUKARYOTIC CELL CYCLEC1. INTERPHASE – 90% cell life – Where the cell spends most of its life
  9. 9. C2. CELL DIVISION (2 TYPES) Mother cell Daughter cells MITOSIS MEIOSIS1. DIVIDE2. # TIMES 1 23. WHERE (humans = all cells) (humans=gonads)4. FUNCTION replace old cells sexual reproduction growth asexual reproduction
  10. 10. Interphase
  11. 11. MITOSISA. PHASES – diploid organism prophase metaphase anaphase telophase & cytokinesis
  12. 12. Prophase1. Chromatin into chromosomes2. Nuclear envelope disintegrates3. Spindle fibers form near the nucleus and some attach to kinetochores4. Centrioles start tomove to opposite poles.
  13. 13. MetaphaseChromosomes line up along the equator.
  14. 14. AnaphaseThe spindle fibers are shortened at the kinetochore whichcauses the chromatids to be pulled apart and moved toopposite poles.
  15. 15. TelophaseChromatids are at opposite poles, start to reform nuclearmembrane, spindle fibers start to disappear.
  16. 16. CYTOKINESISIn animal cells the membrane pinches off to form 2 newcells, reform chromatin and nucleus .
  17. 17. Overall
  18. 18. III. MEIOSIS - generalTwo cell divisions where the resultingdaughter cells have ½ the number ofchromosomes as the originals. 23 23 MI MII 23 46 23 23 23
  19. 19. Prophase I of Meiosis INuclear membrane starts to disintegrate.Chromatin to chromosomes. Centrioles move. Form spindle fibers.Homologous Pairs form chiasma where can get crossing-over (exchange of genetic material) = recombination
  20. 20. Metaphase I of Meiosis IHomologous pairs line up along the equator.Independent Assortment – the chromosomes arrange themselves independent of the other homologous pairs. Type of recombination.
  21. 21. Anaphase I of Meiosis IThe spindle fibers shorten and pull apart the chromosomesof the homologous pairs.
  22. 22. Telophase I of Meiosis IThe chromosomes reach opposite poles and start to form nuclear membrane and disintegrate spindle fibers.
  23. 23. Cytokinesisand start to formThe chromosomes reach opposite poles nuclear membrane and disintegrate spindle fibers. Divide cell contents. The two new cells each contain ½ the number of chromosomes as the original cell (each chromosome has two chromatids).
  24. 24. Prophase of Meiosis IIRe-condense chromosomes if they uncondensed andreplicate the centrioles.Spindle fibers form and centrioles move to opposite poles.
  25. 25. Metaphase of Meiosis IIChromosomes line up along equator.Spindle fibers attached.
  26. 26. Anaphase of Meiosis IISpindle fibers exert force to pull chromatids apart.
  27. 27. Telophase of Meiosis IIChromosomes reach the opposite poles and start to reform nuclear membranes.
  28. 28. CytokinesisSplit the cell contents so that end up with four haploid cells.