Cell division

• Cell division involves forming new cells

  There are 2 main type of division:

  
  

  Mitosis – one diploid cell dividing into two identical diploid cells (for the purpose of growth, repair and replacement)

  
  

  Meiosis – one diploid cell dividing into four haploid cells (non-identical – for the purpose of making gametes)

  
  

  For both types of division, every chromosome (DNA molecule) needs to be copied to then put one copy in each new cell.
• DNA replication: 

  1. DNA unzips and unwinds with the help of enzymes. 
  2. Free nucleotides in the nucleus join to bases on the DNA molecule that now have no partner using the complementary base pairing rule.
  3. This continues down the molecule until the whole thing has been replicated. 
  4. There are now two identical DNA molecules. 

  *Mistakes can happen - mutations
• Mitosis: Formation of new somatic cells for growth, repair, and replacement. This process is also used for asexual reproduction. 

  • From each diploid cell, 2 genetically identical diploid cells are produced. 
• Stages of mitosis: 

  PARENT CELL

  • DNA replication (not mitosis)

  1. Chromosomes align in the middle of the cell
  2. Chromatids separate, go to each end of the cell
  3. Physical division of cell into two identical daughter cells 

  DAUGHTER CELLS
• Meiosis: Formation of new gametes (egg and sperm) for sexual reproduction. 

  • From each diploid ovary or tests (gonad) germline cell, 4 haploid cells are produced. 
• Stages of meiosis: 

  • DNA replication (not meiosis)

  1. Chromosomes line up side by side in cell
  2. First division splits number of chromosomes
  3. Chromosomes align in the middle of the cell
  4. Chromatids separate and go to each end of the cell
  5. Physical division two into four unique daughter cells