CELL CYCLE COMBINED NOTES

• Cell Cycle


  Changes a cell undergoes from the time it is formed until it divides to produce new cells
• Cell Cycle 3 Major Phases


  • Non-dividing phase (G0) (Resting or Quiescent Phase)
  • Interphase (Initial Growth G1), (DNA Synthesis S), (Final Growth G2 Phase)
  • Division (Mitosis and Meiosis)
• Three Phases of Interphase

  • G1
  • S
  • G2
• G1 Phase


  First gap phase, the cell carries out routine metabolic activities
• S Phase


  DNA is replicated (New DNA is synthesized)
• G2 Phase


  Second gap phase, the cell prepares for cell division
• G0 Phase


  Resting cells do not follow the normal pattern of the cell cycle, they remain unstimulated to divide
• Cell Division


  When the cell starts to multiply
• Two Types of Cell Division


  • Meiosis
  • Mitosis
• Meiosis


  • Gametes/Sex cells, 8 stages
• Mitosis

  • Somatic/Autosomal cells, 4 stages
• Why does Meiosis need 8 stages instead of 4? Presence of 2 different gametes, partner (egg and sperm)
• Tetrad


  Chromosome containing 4 arms
• Bivalent


  Combined tetrad
• Chiasma


  Exchange of traits
• Gametes can do Meiosis before the birth of the child
• Activation of gametes during puberty (arrest stage is on Prophase G2)
• Mitosis


  N (one set of chromosomes)
• Meiosis


  1/2 (half the number of chromosomes)
• Trisomy


  Excessive number of chromosomes
• G1 Stage


  Initial growth stage, increased protein (ribosome) production to be used for DNA replication, no observable changes in cell appearance but increased metabolic activities with minimal death in cell
• Growth 0/Quiescent


  The cell is performing its designated function
• Interphase (G1)


  Uncoiling of chromatin, prepares the new set of cells that will prepare them, the cell prepares to divide
• Prophase


  Chromatin condenses to form mitotic chromosomes, pairing of homologous chromosomes
• Metaphase


  Exchange of materials between chromosomes to allow differences for parents and siblings, alignment of chromosomes in the middle plate
• Anaphase


  The chromatids separate, two identical sets of chromosomes move to the poles of the cell
• Telophase


  Nuclear envelopes form around each set of chromosomes, separation of the cytoplasm or cell wall, cleavage furrows, transformation of chromosomes to chromatin
• Propidium Iodide (PI)


  A fluorescent cell cycle stain, the intensity of the PI signal is directly proportional to DNA content
• The cell activity during G1 is regulated by Cyclin E and G1 Restriction Point R will determine if the cell will undergo towards the S phase
• S Stage


  DNA Replication Stage, cells with highly active metabolism will proceed with S stage (irreversible)
• Procedures during S Stage

  • Initiation
  • Elongation
  • Termination
• G2 Stage


  Final Growth Stage, initiation of development of centrioles and rapid synthesis of ribosomes in preparation for cell division, errors in G2 phase are regulated by the p53 protein (tumor suppressing protein)
• Mitosis


  General cell division, the same number of chromosomes, requires only one parent
• Meiosis


  Reproductive system is responsible for the development of haploid cells, reduced number of chromosomes and requires two parents
• Types of Cells in the Human Body

  • Diploid (2n)
  • Haploid (n)
• Diploid


  A combination of maternal and fraternal DNA
• Haploid


  Reduced cell DNA content (for combination), 23 chromosomes
• Chiasma


  Random combination of genes in parents, X chromosome cannot chiasma in Y chromosome, small Y is not compatible with X
• Offspring probability: 50% female, 50% male
• Meiosis I Prophase Stages

  • Leptotene (Condensation of chromosome)
  • Zygote (Pairing of homologous chromosome)
  • Pachytene (Fusing together of chromosomes)
  • Diplotene (Chiasma formation)
  • Diakinesis (Dissolution of nuclear membrane)