Genetically
Modified
Organisms
Tobacco plant with firefly gene © Keith Wood (of
DeLuca lab) for Science Magazine 1986
Bt Maize
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Bacillus thuringiensis
produces a bacterial
toxin (Delta-endotoxin)
The bacterium has been
used as an insecticide
since 1938
It stops the insect from
feeding by attacking the
insect gut lining
© 2010 Paul Billiet ODWS
Image Credit: Bacillus thuringiensis
Cry gene
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The toxin is produced by the
Cry gene
Found on plasmids in the
bacterium
The gene is added to the
genomes of crop plants
using a bacterium that
forms root nodules in plants
(Agrobacterium tumificiens)
Bt crops produced from
1996 onwards: maize,
potato, cotton, soybean
© 2010 Paul Billiet ODWS
Image Credit: GMO Compass
BT Maize
Advantages
Only insects attacking the crop will be
poisoned Environmentally friendly
 All tissues are protected even the roots
 Biodegradable – does not accumulate in
the food chain
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© 2010 Paul Billiet ODWS
Disadvantages
Pollinators may be killed too
 Pesticide resistance in insects is rapid –
but crop management could limit this
 Pollen grains could spread the gene to wild
relatives of the crop plant
– but terminator genes could prevent this
- but terminator genes considered
unethical in developing nations
 Technology expensive
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© 2010 Paul Billiet ODWS
Spider silk
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Spider’s silk is
5 times stronger than a
thread of steel of the
same thickness
3 times stronger than
Kevlar (carbon fibre)
Spiders are carnivores
and cannot be raised
Transgenic animals can
produce the spider
protein
© 2010 Paul Billiet ODWS
© P. Billiet
Aculepeira ceropegia
a European orbweb
spider
Spider silk
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The gene for spider
silk protein was
isolated from the
golden orb weaver
(Nephila clavipes)
Not easy, it is a
fibrous protein so it
has a very repetitive
gene sequence
© 2010 Paul Billiet ODWS
Nephila clavipes © C. Frank Starmer
Web-based kid
Spider goat © Sean O'Neill
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Gene (plus regulator genes) inserted into goat
mammary gland cells
Genetically transformed cells could be made to
secrete spider silk protein
Transformed goat cells fused to enucleated oocyte
Genetically transformed goat embryos produced
© 2010 Paul Billiet ODWS
Goat grows up, females produce spider
silk protein in their milk
 Silk protein purified
 Extruded through nozzle to produce silken
thread
 Not easy as the conditions are not quite
the same a spider’s spinneret
 Transformed goats can be bred together
perpetuating the trait
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© 2010 Paul Billiet ODWS
Applications
Super strong surgery thread
 Artificial ligaments
 Light bullet proof body armour
 Biodegradable fishing line
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© 2010 Paul Billiet ODWS