B13- variation

• Nature genetic variation

  • less variation between family members
  • eye colour, nose shape, sex and dimples are all inherited
• nurture environmental variation

  Conditions developed in can affect genetics

  Genetically identical plants can vary when grown under different light or mineral ion conditions

  Plants deprived of light, co2 or ions are smaller and weaker and don’t reach genetic potential
• Natural selection stages

  1. In a population there is variation caused by mutation
  2. some are better adapted than others
  3. Those that are adapted survive, those that are not adapted die
  4. Survivors pass on their genes/alleles to their offspring
  5. Therefor the gene for adaptation are kept and the genes of the non-adapted organisms are lost
• What is selective breeding

  Selecting the best organisms to breed together to produce offspring with desired features
• Examples of selective breeding

  Disease resistance in crops

  Greater crop yield

  animals that produce more milk/meat

  Domestically desirable dogs

  Brighter coloured flowers
• Process of selective breeding

  Identify 2 organisms with desired features

  Reproduce them together

  Select the offspring with desired features and reproduce the together

  Repeat the process over many generations
• Problems with selective breeding

  -reduces diversity in a population

  -disease Could wipe out a whole population

  -inbreeding increasing risk of recessive genetic disorders
• What is genetic engineering

  Involves changing the genetic material of an organism. A gene is cut out of one organism and placed into the DNA of another organism
• How is golden rice genetically modified

  Golden rice contains added beta carotene which is used to produce vitamin a - vitamin a deficiency lead to blindness
• How is bacteria genetically modified to produce human insulin

  • in a human cell an insulin gene is cut out of DNA using an enzyme
  • a plasmid ring is taken out of bacterium and split open using an enzyme
  • the insulin gene inserted into the plasmid using another enzyme
  • the plasmid with the insulin gene is taken up by bacterium
  • the bacterium multiply
  • The insulin gene is switched on and insulin harvested
• Advantages of genetically modified organisms

  Same risks as non GM crops

  Destroy digestive systems of insect pests

  Better growth rates

  Increased crop values

  Designed to grow well in dry, hot, or cold parts of the world
• Disadvantages of genetically modified crops

  Gene flow (modified and normal crops could mix and make unwanted characteristics)

  Don’t know long term health impacts of GM food

  Don’t know long term environmental impacts of GM crops