Cell Cycle

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• Unit 4
• Cell Cycle Mitosis

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Cell reproduction in multicellular and
unicellular organisms

• Unicellular reproduce by binary fission, asexual
  reproduction
• Multicellular reproduce by cell division
  process of growth and repair depend on cell
  division also involves the production of sex
  cells

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Describe chromosomes

• Carriers of genetic material found in nucleus
• Made up of DNA
• Information is copied and passed to future
  generations
• Usually DNA exists as chromatin which are long,
  winding strands that condense into chromosomes
  before dividing

Animation http//www.johnkyrk.com/chromosomestru
cture.html
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Chromosome structure

• Chromosomes are made up of two chromatids which
  are held together with a centromere
• Human chromosome number is 46 in body cells 23
  in sex cells

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Describe the cell cycle

• Sequence of growth and division in the cell
• Consists of 4 phases
• 1. M phase cell division
• 2. S phase copying of chromosomes
• 3. G1 phase growth phase
• 4. G2 phase growth phase
• Interphase is the growth period where DNA is
  copied includes S, G1 and G2
• Mitosis dividing period producing two new cells
  includes M phase

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List and describe the steps of mitosis

• Mitosis is the division of cells producing two
  cells with the same number of chromosomes

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Prophase

• Longest phase of mitosis
• Chromatin coils into chromosomes
• The nucleus disappears
• Centrioles form and move to opposite poles of
  cell
• Spindle fibers form from centrioles and begins to
  cross cell

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Metaphase

• Chromosomes line up in the middle of the cell
• Spindle now forms across the cell

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Anaphase

• Spindle fibers begin to shorten
• This pulls chromosomes apart
• Now the chromosome halves are referred to as
  chromatids

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Telophase

• Chromatids reach poles
• Chromosomes unwind into chromatin
• Spindle fibers break down
• Nucleolus and nuclei reform
• Plasma membrane begins to pinch in

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Cytokinesis

• Division of cytoplasm
• In animal cells cell membrane continues to pinch
  in until two cells are formed
• In plant cells cell plate forms in center of
  cell and eventually splits cells
• At the end of mitosis, two new cells are
  produced called daughter cells

Animation http//www.johnkyrk.com/mitosis.html