Chapter 12 Genetic Engineering

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Chapter 12Genetic Engineering

• Charles Page High School
• Stephen L. Cotton

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Section 12-1Modifying the Living World

• OBJECTIVES
• Describe breeding strategies that have been used
  to modify living things.

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Section 12-1Modifying the Living World

• OBJECTIVES
• Explain how mutations in organisms can be useful
  to humans.

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Section 12-1Modifying the Living World

• Humans are always trying to improve the world
  around us
• Farmers and Ranchers- have tried to improve the
  organisms with which they work
• select the most productive plants or animals

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Section 12-1Modifying the Living World

• Selective Breeding can increase productivity
• Forms of selective breeding
• inbreeding and hybridization
• Selective breeding is the oldest and most obvious
  way to improve a species

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Section 12-1Modifying the Living World

• A few individuals are selected to serve as the
  parents of the next generation
• these are individuals that have some desirable
  characteristic
• increase milk production in cattle, or certain
  flower colors

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Section 12-1Modifying the Living World

• Luther Burbank (1849-1926) is probably the
  worlds foremost selective breeder
• more than 250 new varieties of fruit, but also
  included other plants such as the daisy and
  famous Burbank potato

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Section 12-1Modifying the Living World

• Once a desirable trait is achieved, the next step
  is to keep it
• Inbreeding is one way to do this
• crossing individuals with similar characteristics
  - purebreds
• often closely related to each other

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Section 12-1Modifying the Living World

• Inbreeding useful but certain risks
• the chances of recessive genetic defects showing
  up is much greater
• deformity in joints blindness in German
  shepherds and golden retrievers from repeated use

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Section 12-1Modifying the Living World

• Hybridization - a cross between dissimilar
  individuals
• may even involve crossing different (but related)
  species
• Hybrids are often healthier than the parents
  this is known as hybrid vigor

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Section 12-1Modifying the Living World

• New hybrids may have a) increased
  disease resistance, b) more yield per acre, and
  c) more nutritional value
• modern hybrid corn produces as much as 10 times
  the yield per acre of older varieties

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Section 12-1Modifying the Living World

• Note Figure 12-2, page 248
• As useful as selective breeding is, it is
  confined to characteristics that already exist in
  the population
• Mutations can produce new inherited
  characteristics

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Section 12-1Modifying the Living World

• If these new characteristics are desirable,
  breeders can use selective breeding to produce an
  entire population that have these characteristics
• But, can we always wait for a beneficial mutation
  to appear?

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Section 12-1Modifying the Living World

• We may increase the chances (artificially) to
  cause a mutation
• done with substances called mutagens
• examples include radiation and certain chemicals

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Section 12-1Modifying the Living World

• Many mutations are harmful but with luck a few
  mutants with desirable characteristics may be
  produced
• Mutagenesis (using mutagens to increase mutation
  rate) is particularly useful with bacteria

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Section 12-1Modifying the Living World

• Their small size allows millions to undergo
  mutagenesis, thereby increasing the chance of
  producing a useful mutant
• many useful strains have been developed, even
  bacteria that can digest oil to help clean up oil
  spills!

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Section 12-1Modifying the Living World

• Note Figure 12-4, page 249 showing a) seedless
  oranges and b) hairless mice