Cell Cycle

• Mitosis is the stage in the cell cycle when the nucleus divides
• We need a cell cycle for:

  • Growth - make new cells
  • Repair - repair cells that are damaged
  • Replace - replace cells that are damaged or dead
• Cell division is when cells separate into two new cells

  
• Interphase - the time when cell is not dividing
• M-phase - cell division by mitosis
• G1 phase:

  • Cell grows
  • Make new proteins eg. enzymes
  • Respires to release energy + increase ATP stores
  • Make new cell structures eg. mitochondria
• S phase:

  • DNA replication
• G2 phase:

  • Same as G1 phase
• DNA replication must take place before cell division so that the cells produced are diploid
• New cells produced are diploid and are all genetically identical
• DNA replication is the process of making two identical copies of DNA in a cell.
• DNA replication:

  • Stage 1 - DNA double helix unzips [cross links between bases break]
  • Stage 2 - Single stranded DNA used as a template
  • - Free nucleotides pair up with exposed complimentary
  • bases [ A-T/G-C]
• Diploid - a cell containing two sets of chromosomes
• Gene - section of a chromosome that codes for a protein
• Stem cell - An undifferentiated/ unspecialised cell that has the potential to become any type of cell/tissue/organ
• Differentiation - The process of cells becoming specialised for a particular function
• Meristem is found in the tips of the roots and shoot tips of plants.
• Specialised cell - A cell which has adapted for its job
• Mitosis stages:

  1. DNA replication
  2. Double armed chromosomes line up along the centre of the cell
  3. They then separate to opposite sides of the cell
  4. Cell divides ( diploid cells!)