CELL DIVISION

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CELL DIVISION mitosis meiosis
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• Forms of DNA
• When the cell is NOT dividing chromatin
• When the cell IS dividing chromosome

Monovalent chromosome
Bivalent chromosome
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• Why do cells divide?
• Replacement - cells wear out die
• Repair - tissues can be damaged by injury or
  infection
• Growth of the organism
• Reproduction

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• Types of cell division
• Mitosis
• New cells are identical to the old cells
• Chromosome number is the same in parent
  daughter cells (diploid -2n)
• Growth, repair, asexual reproduction

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MITOSIS
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• Meiosis
• Parent cell divides twice to produce 4 cells
• Produces gametes (sex cells sperm/eggs)
• Daughter cells have half the original number of
  chromosomes (haploid -1n)

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4.When two gametes join to form a zygote, it will
have the normal of chromosomes
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MEIOSIS
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5. Daughter cells are not Genetically identical
a.) Homologous chromosomes separate, sending one
version of each to the new cells. b.) Crossing
Over sometimes chromosomal segements are
exchanged between Homologous Chromosomes.
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• Phases of Mitosis
• Interphase
• Growth normal cell activities
• DNA chromatin
• as the cell prepares for division, DNA is
  duplicated

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• Prophase
• Chromatin thickens reveals duplicated
  chromosomes (bivalent)
• Centrioles move to poles
• Nuclear membrane dissolves

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• Metaphase
• Bivalent chromosomes line up along equator of
  cell
• Chromosomes attach to spindle fibers

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• Anaphase
• Spindle fibers pull monovalent chromosomes to
  opposite ends of cell
• an identical set of chromosomes moves to each
  pole

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• Telophase
• Chromosomes uncoil become chromatin again
  Nuc. Memb Reforms
• Cytokinesis cell membrane pinches in to form 2
  separate cells

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• Phases of Meiosis
• Cells go through two rounds of division during
  meiosis, resulting in 4 haploid cells

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Meiosis I II
Section 11-4
Diff. genes
Same genes