Download Chapter 10

Selective Breeding
 Over 1000’s of years mankind has
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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
Genetic engineering
 Each bacterial cell has a
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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.g
insulin
Genetic Engineering v Selective Breeding
 Both can alter the genetic makeup of a species for
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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
Genetic Engineering v Selective Breeding
 Genetic Engineering
 Allows scientists to directly alter the genotype of a
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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
Applications of Genetic Engineering
 Medical – insulin, growth hormone,
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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
Transgenic multicellular organisms
 Genetic engineering on more
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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
Transgenic Plants
 Plants that have gained new
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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
Transgenic organisms - future
 Cereals : crops will be modified to contain genes for
certain characteristics
 e.g resistance to herbicides, drought, pests, microorganisms & salinity
 - increased photosynthetic rate
 Future - animal genes into plants e.g already
haemoglobin grown in tobacco plants