The Cell Cycle - Chapter 11 AQA AS Biology

Chapter 11 - AQA AS Biology

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  • Created by: H.N
  • Created on: 28-12-12 14:36
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  • The Cell Cycle
    • Replication of DNA
      • ensures all daughter cells have correct info to produce enzymes + proteins they need
      • cell division - whole cell divides (follows nuclear division)
      • semi- conservative replication
        • requirements
          • 4 types of nucleotides each with their bases of A, G, C + T must be present
          • both strands of DNA must act as a template for attachment of nucleotides
          • DNA polymerase - castalyse reaction
          • source of chemical energy - to drive process
        • the process
          • 1. enzyme DNA Helicase breaks H bonds linking the base pairs of DNA
            • 2. double helix separates into 2 strands + unwinds
              • 3. energy activates these nucleotides
    • Mitosis
      • takes place when cell is NOT dividing = INTERPHASE
      • continuous process
      • 4 stages:
        • 4. TELOPHASE = chromatids reach poles, become indistinct, nuclear envelope + nucleolus reform, spindle disintegrates
      • importance
        • produces  2 daughter nuclei that have the same  no. of chromosomes as the parent cell + each other
        • Growth
        • Repair
        • differentiation
    • the cell cycle
      • 1) INTERPHASE
        • occupies most of the cell cycle, no division takes place.
        • split into 3 parts
          • 1. 1st Growth  (G1) phase - cell grows, more organelles produced + proteins made
            • 2. Synthesis (S) phase - DNA replicated
              • 3. 2nd Growth (G2) phase - organelles grow + divide, energy stores increased
      • 2) NUCLEAR DIVISION
        • nucleus divides either into 2 (mitosis) or 4 (meiosis)
      • 3) CELL DIVISION
        • whole cell divides into 2 (mitosis) or 4 (meiosis)
      • length of complete cell cycle varies amongst organisms
      • cancer
        • group of diseases caused as a result of damage to genes that regulate mitosis + the cell cycle
        • leads to uncontrolled growth of cells
        • abnormal group of cells = tumor - can develop in any organ of the body
  • 4. TELOPHASE = chromatids reach poles, become indistinct, nuclear envelope + nucleolus reform, spindle disintegrates

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