cell division and stem cells

• Chromosomes

  The structure made of DNA that codes for all the characteristics of an organism
• DNA

  The part of the cells of living things that carries information about how they look and function
• Genes

  The basic unit of genetic material inherited from our parents. A gene is a section of DNA which controls part of a cell's chemistry - particularly protein production
• Mitosis

  1. Cell division which ensures that, when a cell divides, each new cell produced has the same genetic information

  2. Produces two daughter cells identical to the parent cell
• Each human body cell contains 46 chromosomes, arranged into 23 pairs
• Cell division


  • Occurs when an organism grows, needs to replace worn-out cells, or repair damaged tissue
• Cancerous cells


  Begin to grow and divide uncontrollably, producing new cells even if the body does not need them
• Tumour


  A lump of cells formed as a result of uncontrolled cell division
• Carcinogen


  A chemical or other agent that causes cancer
• Mutation


  A random and spontaneous change in the structure of a gene, chromosome or number of chromosomes
• Risk factors for cancer


  • Lifestyle factors (viruses, chemicals, radiation, diet)
  • Industrial and environmental factors (radiation, chemicals)
• A single mutation will not cause cancer - several are required
• We are more likely to develop cancer as we get older
• Certain genetic factors increase the likelihood of developing some cancers
• Meiosis


  Cell division that produces genetically varied daughter cells with half the number of chromosomes
• Meiosis


  • Copies of the genetic information are made
  • The cell divides twice to form four gametes, each with a single set of chromosomes known as haploid cells
  • All gametes are genetically different from each other, they show variation
• Stem cells


  Cells that can differentiate into specialised cells during the development of organisms
• Sexual reproduction


  The formation of a new organism by combining the genetic material of two organisms
• Gamete


  Sex cell (sperm in males and ova/eggs in females)
• Zygote


  A fertilised egg cell
• Embryo


  An organism in the early stages of development
• Chromosome


  The structure made of DNA that codes for all the characteristics of an organism
• Stem cells


  Cells found in foetuses, embryos and some adult tissues that can give rise to a wide range of other cells
• Differentiation


  When an unspecialised cell becomes a more specialised cell type
• Specialised cell


  A cell that has become differentiated to carry out a particular function, eg red blood cell
• Embryonic stem cells


  • Cells removed from the embryo that will differentiate into any cell type
• Adult stem cells


  • Stem cells that remain in the bodies of adults and can differentiate into related cell types only
• Therapeutic cloning


  Using cloning technology for medicinal purposes, e.g. to use a person's DNA to clone one of their organs for use in transplanting
• Stem cells can divide to produce new cells, which can then divide into different cell types
• Stem cells have the potential to be transplanted into patients to treat medical conditions and disease
• Stem cells could be used to replace cells that have been damaged or destroyed, e.g. in type 1 diabetes, multiple sclerosis, spinal cord or brain injury
• Potential sources of stem cells


  • Embryonic stem cells
  • Adult stem cells
• Embryonic stem cells can differentiate into a wider range of cell types, but are difficult to obtain
• Adult stem cells will differentiate into a narrower range of cell types
• Bone marrow transplants are an example of adult stem cell transplant
• Bone marrow cells will differentiate into different types of blood cells
• Bone marrow transplants are carried out in cases of blood cell cancer, e.g. leukaemia and lymphoma, or when blood cells have been destroyed, e.g. during cancer treatment
• Benefits of using your own stem cells


  • No rejection
  • No need to find a donor
  • No need for tissue typing
• There are clinical, ethical and social issues associated with the use of stem cells in medicine
• Clinical issues with stem cell use

  • No guarantee of success
  • Difficulty finding suitable stem cell donors
  • Difficulty obtaining and storing a patient's embryonic stem cells
  • Mutations observed in cultured stem cells
  • Potential for stem cell contamination with viruses