Nov 13 - University of San Diego

deadstructureBiotechnology

Dec 14, 2012 (4 years and 9 days ago)

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I.
Genetic Engineering


D.
Drawbacks


Opponents emphasize failures of
technology, potential environmental harm


“Frankenfood”


“Farmageddon”

1.
Harm to native species through competition


Transgenic organisms could be superior competitors


Potential route to extinction for native species

2.
Damage to beneficial insects


Ex



Evidence that ladybugs and lacewings suffer (shorter lifespan,
reduced reproduction) when fed aphids and caterpillars that had fed on
GM potatoes and corn, respectively

3.
Damage to soil community


Certain GM crops could reduce activity of soil fungi and microbes


Negative impact on nutrient cycling in the soil

4.
Release of resistance genes


Could potentially lead to “super weeds” if resistance genes get
transferred to weedy species


Could harm non
-
GM agriculture, including organic farming through pollen
drift

5.
Upset natural balance of ecosystems


Could result from release of GMOs or hybridization between GMOs and
native species


Ex



GM rape can crossbreed with wild turnips, passing herbicide
tolerance to offspring


Potential solution = “
Terminator technology


I.
Genetic Engineering


E.
Trends


125 GM agricultural plants approved for
growth in the U.S. (ISAAA)


Most designed to

1)
Reduce pest damage

2)
Confer resistance to herbicides, pesticides,
viruses, other pathogens

3)
Reduce crop spoilage

Genetically modified crop traits tested

in developed countries, 1987

2000

I.
Genetic Engineering


E.
Trends


US grows ~48% of GM crops worldwide
(acreage basis)


2012: corn 88%, cotton 94%, soy 93% GM


Other major growers of GM crops

1)
Brazil

2)
Argentina

3)
India

4)
Canada

5)
China

www.ers.usda.gov/data
-
products/adoption
-
of
-
genetically
-
engineered
-
crops
-
in
-
the
-
us/recent
-
trends
-
in
-
ge
-
adoption.aspx

I.
Genetic Engineering


F.
Examples

1.
Bollgard
®

and Bollgard II
®

Cotton


Both strains express insecticidal protein isolated from
Bacillus thuringiensis

(Bt)


Safe


Farmers can spray with Bt toxin and still label
produce as organic


Low toxicity to most non
-
target organism types


Low persistence


breaks down readily


Bollgard II
®

has
stacked traits

to enhance effectiveness


Controls bollworms, budworm


Year 2000


United States averages


Cotton fields planted with Bollgard
®

sprayed 3.9
times less often
vs.

conventional fields


Reduced total pesticide use by 2.7 million pounds


Pest control cost less
-

$15.43/acre


Higher production
-

37 pounds/acre


Higher profit
-

$39.86/acre


Concern



Development of resistance by insect pests

I.
Genetic Engineering


F.
Examples

2.
Golden Rice


GM rice containing genes that produce beta
-
carotene


Can be converted to vitamin A


Vitamin A deficiency (VAD) may cause weakened immune
systems, partial to total blindness, and increased chance of
death


VAD causes 350,000 cases of blindness and has been
linked to 1 million+ deaths each year


Highly controversial

a.
Proponents


Reduce incidence of blindness and other VAD related
health disorders


1/2 lb of rice/day will keep VAD symptoms away

b.
Opponents


Nutritional deficiencies will prevent people from absorbing
beta
-
carotene from rice


Concentrations of beta
-
carotene in rice are low, and an
average woman would need to eat 16 lbs of golden rice a
day to get 100% of daily requirement


Alternatives like leafy green vegetables or unpolished rice
are better, cheaper sources of vitamin A


Western corporations are trying to control rice production

I.
Genetic Engineering


F.
Examples

3.
Future GM crops


SmartStax
TM

corn


Pest resistant, herbicide tolerant


Bt rice


Pest resistant


High omega
-
3 soybeans


Enhanced nutrition


RR Sugarbeets*


Herbicide tolerant


2007: <10% of US


2009: 95% of US


Blue roses


Ornamental

I.
Genetic Engineering


G.
Benefits and Risks

1.
Benefits


Accelerated improvement of crop strains

a.
Elevated yields, either per plant or per acre


Usually involves inserting growth factor


Plants grow larger, faster or both


Con



Accelerated growth may alter chemical
composition


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Increased yield per acre, more crops per year


Con



Plants produce different compounds at
different life stages


Young plants tend to produce more irritants and
toxins (self defense)


Potential to cause digestive or allergic problems

I.
Genetic Engineering


G.
Benefits and Risks

1.
Benefits

c.
Increased resistance to disease, pests, toxins


Reduced losses


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Reduced application of chemicals


Con



Potential transfer of resistance genes to
weedy plant species through pollination


Less problematic in areas where crop plants don’t
have wild relatives


Con



Development of resistance in pests

d.
Increased longevity of harvested produce


Resistance to spoilage


Ex



Potato engineered with bacterial gene for
antifungal properties


Helps potatoes to stay in storage without rotting


Con



Chemicals that resist decomposition likely to
be more difficult to digest

I.
Genetic Engineering


G.
Benefits and Risks

1.
Benefits

e.
Increased resistance to cultural extremes


Ex



Insertion of Arctic flounder antifreeze protein
genes into strawberry


Confers greater frost resistance and better fruit
storage properties


Con



Potential transfer of antifreeze genes to weedy
plant species

f.
Increased nutritional value


Ex



High starch potato that absorbs less oil when
cooking (low fat potato chips)


Ex



Canola oil (Laurical
®
) with healthier
composition


Con



Unknown effects of eating modified foods


Ex



Insertion of Brazil nut gene into soybeans to
increase protein content


Many people allergic to Brazil nuts

I.
Genetic Engineering


G.
Benefits and Risks

1.
Benefits

g.
Reduced dependence on chemical fertilizers


More efficient growth


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American farmers spend >$12 billion a year on
chemical fertilizers


50% or more of fertilizer applied to crops is not
absorbed and enters runoff


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Con



Transfer of genes for greater growth
efficiency to weeds could be disastrous


Con



Substitution of dependence on big
western agribusiness


I.
Genetic Engineering


G.
Benefits and Risks

2.
Risks

a.
Unexpected effects


May or may not be beneficial


Ex



Klebsiella planticola

(soil bacterium) engineered
to transform plant residue into ethyl alcohol (fuel)


GM strain in soils produced EtOH, leading to
poisoning of grasses and decrease in populations of
beneficial mycorrhizal fungi


Ex



Pseudomonas putida

(bacterium) engineered to
degrade 2,4
-
D (herbicide)


Breakdown products highly toxic to fungi, including
mycorrhizae


Ex



Bacillus thuringiensis

(Bt) toxin may bind to soil
particles, slowing degradation and maintaining
toxicity for longer than expected