B3g: NEW GENES FOR OLD

SELECTIVE BREEDING
1. When humans artificially select the plants or animals that are going to breed. Organisms are selectively bred to develop the best features
  1. Maximum yield of mean, milk, grain etc
  2. Good health and disease resistance
  3. Temperament
  4. Speed
  5. Attractiveness
2. Method
  1. Select best characteristics from existing stock
    1. Breed them together
      1. Select the best of the offspring & breed them together
        Continue until the desirable gene gets stronger and stronger
3. Main drawback: REDUCTION IN GENE POOL
  1. Reduces the number of different alleles because of inbreeding
    1. Can cause health problems: more chance of harmful genetic disorders when gene pool is limited
      1. This is because lots of genetic conditions are recessive (you need two alleles to be the same) - inbreeding means that recessive alleles are more likely to build up
        There can also be problems if a new disease appears: not much variation = if one suffers it is likely that the others will
GENETIC ENGINEERING
1. Moving genes from one organisms to another so that it produces useful biological products
  1. Advantage: you can produce organisms with new and useful features very quickly
  2. Risk: the inserted gene might have unexpected harmful effects
    1. EG: genes are often inserted into bacteria so they produce useful. If these bacteria mutated and became pathogenic, the foreign genes might make them more harmful and unpredicatable
    2. People also worry about the engineered genes 'escaping' - e.g. weeds could gain rogue genes from a crop that's had genes for herbicide resistance inserted into it
2. Method
  1. The gene that codes for the desirable characteristic is selected
    1. It is then cut out (using restriction enzymes) and isolated
      1. The useful gene is inserted into the DNA of another organism
        The organism then replicates and soon there are loads of similar organisms all producing the same thing
3. EXAMPLES
  1. Putting beta-carotene (contains vitamin A) from carrot plants into rice plants
    1. In places in the world which rely heavily on rice for food, vitamin A deficiency is a problem because rice doesn't contain much vitamin A
  2. Human insulin into bacteria
    1. The bacteria are cultured in a fermenter, and the human insulin is extracted from the medium as they produce it
  3. Herbicide resistance into useful plants such as crops
    1. Some weed-like plants have resistance to things like herbicides, frost damage and disease - so it is put into crops
4. MORAL AND ETHICAL ISSUES
  1. Some people think it's wrong to genetically engineer other organisms purely for human benefit, particularly animals, especially if the animal suffers
  2. People worry that we won't stop: in the future those who can afford genetic engineering might be able to decide characteristics of their children, and those who can't may become a 'genetic underclass'
  3. The evolutionary consequences are unknown, so some people think it's irresponsible to carry on when we're not sure what the impact of future generations might be

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B3g: NEW GENES FOR OLD

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