Chapter 2: cell division and differentiation

• Cells are continually lost to make new cells in the body during cell division
• Reasons for cell division

  • Replace worn out cells
  • Repair damaged cells
• Key terms related to cell division and growth

  • Cell division
  • Growth
  • Differentiation
• Cells are diploid (have two copies of each chromosome)
• DNA


  A polymer made up of strands forming a double helix
• DNA structure


  • Sugar phosphate backbone
  • Nitrogenous bases forming the rungs of the ladder
  • Base pairing held by hydrogen bonds
• Alleles


  Different forms of the same gene
• Cell division - Mitosis

  1. Cell replicates chromosomes

  2. Cell divides to form genetically identical daughter cells
• Cell differentiation


  Specialisation process where unspecialised cells become specialised
• Zygote


  Fertilised egg cell, divides by mitosis into an embryo
• Stem cells


  Undifferentiated cells that can become differentiated
• Plant growth


  1. Cell division in meristem

  2. Cell elongation

  3. Cell differentiation
• Meristem


  Region where cell division takes place, found in tips of roots and shoots
• Embryonic stem cells


  Stem cells from 4-5 day old human embryos that are not yet specialised and can grow into any cell type
• Adult stem cells


  Stem cells that remain in the bodies of adults and can differentiate into specialised cells of the tissue where they are found, to replace body cells that die
• Embryonic stem cell research has been controversial due to ethical concerns
• Creating stem cells from patient's own cells

  1. Nucleus removed from patient's cell

  2. Egg cell stimulated to grow into embryo

  3. Stem cells grown from embryo