Rai

• Cell Cycle


  Process of cell growth and division in eukaryotes that is divided into phases based on what is happening in the cell at a given time

  
• Interphase


  The cell is engaged in growth and metabolic activities and can be further broken down into three discrete phases called G1, S, and G2

  
• G1 Phase


  1. Cell grows

  2. Chemical checkpoint controls whether the cell will divide, delay division, or enter a resting stage

  3. If conditions are right, the cell will enter the S phase

  
• S Phase

  1. DNA replication occurs producing two copies of each chromosome

  2. Centrioles help organize cell division
• G2 Phase

  1. After DNA replication is complete, the cell continues to grow and prepare for cell division

  2. At a checkpoint, the success of DNA replication is assessed

  3. If all is well, the cell enters the M phase
• G0 Phase


  • Cells are in a quiescent (inactive) stage that occurs when cells exit the cell cycle
  • Cells that never or rarely divide, like mature cardiac muscle and nerve cells, remain in G0 permanently
• Cell Cycle Checkpoints

  • G1 checkpoint - check for nutrients, growth factors, and DNA damage
  • G2 checkpoint - check for cell size and DNA replication
  • Metaphase checkpoint - check for chromosome spindle attachment
• M Phase


  A complex series of events that move the DNA so that a complete set of genetic instructions will be sent to each daughter cell
• Mitosis

  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Mitosis


  • When the nucleus divides
  • Cytokinesis - when the cytoplasm divides
  • Results in two daughter cells that are identical to each other and the original cell
• Prophase

  1. Chromatin condenses into chromosomes

  2. Spindle fibers form and the nucleolus and nuclear membrane disappear
• Metaphase


  Spindle fibers align the chromosomes along the equator of the cell
• Anaphase


  The spindle fibers separate sister chromatids into two separate groups of chromosomes pulling them toward the poles
• Telophase


  The nucleolus and nuclear membrane reform, the chromosomes disperse into chromatin
• Cytokinesis

  1. The division of the cytoplasm

  2. In animal cells, the cell membrane progressively pinches the cytoplasm until two identical daughter cells form

  3. In plant cells, cell wall material assembles along the equator forming a cell plate that grows until it joins with the existing cell membrane, separating the two halves of the cell into daughter cells

  
• The M phase of the cell cycle always results in two daughter cells that are genetically identical to each other and the original cell