Topic 4

• Tissue Culture


  Growing cells on an artificial growth medium to reproduce tissue from an individual, without the lengthy process of selective breeding
• Growing plants via tissue culture

  1. Choose plant to clone

  2. Take small pieces of tissue from parent plant

  3. Grow tissue in growth medium with nutrients and hormones

  4. Move growing shoots and roots to potting compost
• Whole plants can be grown via tissue culture
• Plants grown via tissue culture are clones - genetically identical organisms
• Tissue culture allows creation of lines of clones with the same beneficial features
• Animal tissue culture for medical research

  1. Extract tissue sample

  2. Separate cells using enzymes

  3. Place cells in growth medium in culture vessel

  4. Allow cells to grow and multiply

  5. Split cells into separate vessels for further growth

  6. Store tissue culture for future use
• Whole animals are not grown via tissue culture
• Animal tissue culture allows studying effects of substances/environmental changes on isolated cells without complications from whole organism
• Selective Breeding


  Artificially selecting the best plants or animals to breed together to get the best possible offspring and maintain the genes for particular characteristics in the population
• Selective Breeding


  1. Select organisms with desired characteristics

  2. Breed them together

  3. Select best offspring

  4. Repeat over generations to strengthen the desirable trait
• Selective breeding is useful in agriculture and medical research
• Disadvantages of Selective Breeding

  • Reduces gene pool and increases inbreeding
  • Can cause health problems from inheriting genetic defects
  • Reduces resistance to new diseases
• Fossils provide evidence that humans evolved from a common ancestor with chimpanzees around 6 million years ago
• Hominid fossils show characteristics between apes and humans, demonstrating human evolution
• Ardi fossil (4.4 million years old)


  • Climbed trees, had ape-like features but walked upright
  • Brain size similar to chimpanzee
• Lucy fossil (3.2 million years old)

  • More human-like than Ardi, with arched feet adapted for walking, larger brain size
• Turkana Boy fossil (1.6 million years old)


  • More human-like features, larger brain size similar to modern humans, better adapted for walking upright
• Stone tools found provide evidence of human evolution and increasing complexity over time
• Genetic engineering


  Modifying an organism's genome (DNA) to introduce desirable characteristics
• Genetic engineering


  • Relatively new area of science (began in the 1970s)
  • Has many exciting possibilities
• Areas where genetic engineering is useful

  • Agriculture
  • Medicine
• Genetic engineering in agriculture

  • Crops can be genetically modified to be resistant to herbicides
  • Increases crop yield
• Genetic engineering in medicine

  • Bacteria can be genetically engineered to produce human insulin
  • Researchers have transferred human genes that produce useful proteins into sheep and cows
• Process of genetic engineering

  1. Cut up DNA or join DNA pieces together using enzymes

  2. Use vectors (plasmids or viruses) to insert DNA into other organisms
• Genetic engineering has risks as well as benefits
• Concerns about growing genetically modified crops include: escaped genes, effects on food chains and human health
• Concerns about genetic engineering of animals include: unpredictable effects, health problems
• Genetically modified organisms (GMOs) are also known as GM organisms or GMOs
• Reasons why GMOs are useful

  • Help provide food for people suffering from hunger
  • Crops can be genetically modified to be resistant to insects
  • GMOs can be used to provide more food for people
• Bt toxin


  Toxin produced by a bacterium that kills many insect larvae harmful to crops
• The long-term effects of exposure to Bt crops are not yet known
• There is a danger that insects will develop resistance to the Bt toxin
• The world's population is rising quickly and global food production must increase to ensure food security
• GM crops can help increase food production, e.g. crops resistant to pests or drought
• Some argue that people go hungry because they can't afford food, not because there isn't enough food
• There are fears that countries may become dependent on companies who sell GM seeds
• Poor soil is sometimes the main reason why crops fail, and even GM crops won't survive
• Other techniques to increase food production

  • Applying fertilisers
  • Biological pest control methods
• Excess fertilisers can cause problems in rivers and lakes through eutrophication
• Biological pest control can have longer-lasting effects than chemical pesticides and be less harmful to wildlife, but introducing new organisms can cause problems