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Selective Breeding

Selective Breeding. Over 1000’s of years mankind has grown plants and domesticated animals. Characteristics have been selected for repeated breeding e.g - milk yield in cattle - meat yield in poultry and cattle - woolly fleece in sheep - corn seeds with high oil or protein content

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Selective Breeding

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  1. Selective Breeding • Over 1000’s of years mankind has grown plants and domesticated animals. • Characteristics have been selected for repeated breeding • e.g - milk yield in cattle • - meat yield in poultry and cattle • - woolly fleece in sheep • - corn seeds with high oil or protein content • Only members of a species with the required characteristic are allowed to breed

  2. Genetic engineering • Each bacterial cell has a chromosome and a plasmid • Plasmid and chromosomes are made of genes • Each gene makes one protein • - e.g enzyme • Cell activity depends upon chromosomes • BUT new genes can be added to the plasmid • Reprogrammed cell can express an inserted gene e.ginsulin

  3. Genetic Engineering v Selective Breeding • Both can alter the genetic makeup of a species for scientific benefit • Selective Breeding • Requires years of careful selection & breeding • Doesn’t always produce the ideal organism • Only animals that would normally produce the required product can be used

  4. Genetic Engineering v Selective Breeding • Genetic Engineering • Allows scientists to directly alter the genotype of a species • - suited to mankind’s needs • Species can be programmed to make products previously only made by another species • Much easier & cheaper to mass produce bacteria cells (than other species) • Mass quantities of a useful product e.g insulin can be produced

  5. Applications of Genetic Engineering • Medical – insulin, growth hormone, factor VIII • Commercial - • - Bacterial enzymes in detergents to digest stains • - Bacteria produce antifreeze (ethylene glycol) • - Yeast for beer making • - can be modified to produce more alcohol, but fewer carbs • - Cheese making: • - rennin curdles milk (rennin from calves stomach) • - rennin now produced by yeast cells

  6. Transgenic multicellular organisms • Genetic engineering on more complex organisms • Agrobacterium tumefaciens • - bacterium injects a plasmid into plant tissue • - ‘natural genetic engineer’ • Genetic material from plasmid is incorporated into the plants DNA. • Plant expresses bacterial genes • Scientists have altered the plasmids to insert useful genes into the plant DNA • These are Transgenic plants

  7. Transgenic Plants • Plants that have gained new genetic material from foreign DNA • Benefits to plants have included: • - extended shelf life in apples & tomatoes • - resistance to weedkiller in soya crops • - pea plants that produce their own insecticide

  8. Transgenic organisms - future • Cereals : crops will be modified to contain genes for certain characteristics • e.g resistance to herbicides, drought, pests, micro-organisms & salinity • - increased photosynthetic rate • Future - animal genes into plants e.g already haemoglobin grown in tobacco plants

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