4.2 Cell division and stem cells

• Chromosome


  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
• Gene


  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. Each chromosome in a pair carries the same types of genes
• Reasons for cell division


  • Organism growth
  • Replacing worn-out cells
  • Repairing damaged tissue
• Cancerous cell


  A cell that begins to grow and divide uncontrollably, producing new cells even when the body does not need them
• Tumour


  The 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
• A single mutation will not cause cancer - several are required. This is why we are more likely to develop cancer as we get older
• There are certain genetic factors that increase the likelihood of developing some cancers
• Risk factors for cancer


  • Lifestyle factors
  • Viruses linked with cancer
  • Chemical carcinogens
  • Alcohol intake
  • Exposure to ultraviolet radiation
  • Poor diet
  • Industrial and environmental factors
• Exposure to ionising radiation, like ultraviolet radiation in sunlight, increases the risk factor for cancer
• Exposure to chemical carcinogens such as those in cigarette smoke increases the risk factor for cancer
• Mitosis


  Cell division for growth and repair, produces genetically identical daughter cells with a full set of chromosomes
• Meiosis


  Cell division for sexual reproduction, produces genetically varied daughter cells with half a set of chromosomes
• Stem cells


  Cells that can differentiate into specialised cells during organism development
• Stem cells in plants
• Two parents are needed


  For sexual reproduction
• Gamete

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


  Fertilised egg cell
• Chromosome


  Structure made of DNA that codes for all the characteristics of an organism
• Embryo

  Organism in the early stages of development
• Gametes are formed by meiosis
• Gametes in animals are sperm and eggs
• Gametes in flowering plants are pollen and eggs
• Meiosis

  1. Copies of genetic information are made

  2. Cell divides twice to form four gametes, each with a single set of chromosomes (haploid cells)

  3. All gametes are genetically different from each other, showing variation
• Stem cell therapy is the use of stem cells to treat or prevent diseases.
• Embryonic stem cells are derived from embryos, while adult stem cells come from various tissues such as bone marrow, blood, skin, fat, liver, brain, heart, pancreas, and umbilical cord blood.
• The use of embryonic stem cells raises ethical concerns due to their origin from human embryos.
• Embryonic stem cells have unlimited potential and can develop into any type of body cell, making them more versatile than adult stem cells.
• Adult stem cells can be used to repair damaged tissue but have limited potential compared to embryonic stem cells.
• 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
• 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