Transcript ANDREW SAYER BARRY TWIDALE

Genetically Modified Crops
Science and Concerns
Andrew Sayer and Barry Twidale
April 2002
What Is Genetic Modification?
• What does Genetic Modification
actually mean?
• Until recently very few people
knew what genetic engineering
was.
• Today it is well heard of although
not necessarily fully understood by
the majority of the British public.
• This has led to fears amongst
consumers over what is actually
being introduced into their food
[1].
• Essentially, Genetic modification
is advertised as being the same as
selective breeding (used for
century’s) only much quicker.
• An organisms characteristics are
determined by its DNA.
• DNA is the genetic code from which
RNA and subsequently all the
features of a living organism are
produced.
• Products such as a specific protein
are coded for by a specific gene.
Chains of genes are what make up
the whole genetic code of the
organism.
• Genetic modification of plants is the
removal or insertion of a specific
gene for a specific product, from
another organism, into the plants
genetic code , altering the plants
properties [2].
Why Genetically Modify?
• Pest control. Pests (opposite) can drastically reduce
crop yields, even resulting in complete crop destruction
[3].
• Increased yields. It is predicted that current farming
methods will not meet population demands by 2020 [4].
• Reduction in chemical usage. Pesticides and
insecticides contribute greatly to water pollution.
• Increased nutritional value.
• Improvement of sensory attributes. Increased
consumer desire, (organoleptic quality) [5].
• Increased company profit. Higher sales due to greater
desire and demand.
• Cheap food supplies. For the third world and a
growing population.
Fig 1. Source: www.uky.edu/Agriculture/Entomology/entfacts/veg/ef304.htm
Fig 1. Some common
plant pests. Aphids
(top), Wire-Worm
(middle) and Colorado
Beetle (bottom).
Who’s involved ?
The Major Players:
• Monsanto (US).
The Products:
• Flavr Savr Tomato, (slow ripening).
• DuPont.
• Novartis (Swiss).
• Astra Zeneca (UK).
• Pioneer Hi-bred International
(US).
• Seminis (US). Control 38% US
crop seed market and 24%
European seed Market.
• Agrevo (UK) [6].
Fig 2. The Flavr Savr Tomato
Source
http://www.ca.uky.edu/agripedia/glossary/agriart/
tomato.jpg
• Insect resistant potatoes and cotton.
Herbicide resistant soybeans,
rapeseed oil and various other crops
[6, 7].
The GM Process
1. Agrobacterium
Tumerfaciens bacterium.
2. Removal of Ti Plasmid,
and DNA cutting with
restriction enzymes.
3. Foreign DNA cut by
same restriction enzymes.
4. Foreign DNA inserted
into Ti Plasmid.
5. Modified Plasmid reinserted into bacterium.
6. Bacterium is used as a vector for insertion of the new gene into the plant cell.
7. The cells containing the new gene are grown on a culture.
8. The cell clones are used to generate new plants carrying the foreign gene.
Antibiotic Resistant Markers
Not all Bacteria are transformed (i.e. accept the modified
Plasmid). To test which bacteria contain the modified Plasmid
(new DNA) the following test is performed.
•1. Agrobacterium
Tumerfaciens
•2. Extract Ti Plasmid
•3. Add new DNA
•4. Add Ampicillin
resistant DNA
•5. Re-circularise the
Modified Plasmid.
•6 Re-insert plasmid which contains genes for both the desired product and
ampicillin resistance.
•Grow on ampicillin plates. Those cells that grow are able to do so by expression
of the ampicillin resistance gene hence have taken up the new DNA.
Genetically Modified Potatoes.
1. Plasmid DNA is cut with
restriction enzymes at the
recognition sites (specific for each
particular enzyme).
2. Sticky ended DNA fragments
produced.
3. DNA from the snowdrop genome
is cut with the same restriction
enzyme, creating the same sticky
ended fragments.
4. The Plasmid and Snowdrop DNA
are annealed together.
SOURCE: Tortora, Funke and case, (2001). [7]
5. The Plasmid is re-circularised and
re-inserted into the bacterium, (see
previous slide point 5). This is then
used to infect potato cells.
Case Study, Pusztai’s Potatoes.
Arpad Pusztai is a molecular biologist
who worked at the Rowett research
institute in Scotland.
Pusztai Spliced the Lectin gene (from
snowdrops) into potato DNA (see
diagram) in an attempt to confer selfproduced insect resistance for the
potato.
•Pusztai conducted trials where rats
were fed potatoes containing the Lectin
gene.
•1 group of rats were fed ordinary
potatoes
•1 group of rats fed ordinary potatoes
with Lectin sprinkled on top.
•1 group of rats fed potatoes with the
Lectin gene spliced into its DNA.
Source: Despatches. Investigation into the safety of GM foods. 11-03-99. [8]
Case Study, Pusztai’s Potatoes.
Arpad Pusztais Results
•
•
Only the third group of rats which had been fed genetically modified potatoes became ill.
The rats showed organ and brain damage as high as 15% compared to the healthy rats.
In fact, Pusztai presented his results as
“overall effect devastating.”
•He publicly presented his results in 1998 on
Television as he felt this finding was vitally
important.
•Initially the findings were appraised by fellow
members of the research institute. However,
their feelings rapidly changed towards Pusztai’s
results.
•Professor James, Head of the Rowett claimed
Pusztai was “muddled and there were failings in
http://www.naturalscience.com/ns/cover/cover8.html
his research methods.”
•Pusztai was sacked from the Rowett 2 days after he presented his results.The Rowett also
rapidly produced an audit of Pusztai’s work which refuted his findings.
•Source: Despatches. Investigation into the safety of GM foods. 11-03-99 [8]
Case Study, Pusztai’s Potatoes.
Pusztais Concerns
Protein Interaction
Gene Interaction
Pusztai was concerned that interactions
may take place between the products
from both the natural potato DNA and
the inserted Lectin gene.
It is possible that insertion of the
Lectin gene may cause genes
elsewhere in the genome to start
coding for different proteins.
Source: Despatches. Investigation into the safety of GM foods. 11-03-99 [8].
GM Issues and Concerns
Many Issues have been raised over the process of Genetic modification, but are the public
right to be so cynical. It’s not surprising that the UK consumer is beginning to doubt the
safety of what we eat, considering the media coverage of the food industry essentially over
the last 10 years.
Issue
•Cauliflower Mosaic Virus (CMV)
Promoter
•Antibiotic resistance marker genes
•Cross Pollination
•Terminator genes
Concern
In order for ‘new’ genes to be expressed
they require a promoter. 90% of GM
crops use the CMV promoter. However, 1/5th of
all cancers are caused by viruses [8].
There are fears that the genes which confer
antibiotic resistance to the test bacteria could
potentially be passed on to pathogenic bacteria
[3, 9, 10].
Possible production of a species of genetic
superweed, which is resistant to pesticides [4].
Terminator genes can be used to ensure a sterile
GM crop is produced. However, for third world
countries this is impractical as they cannot
afford to purchase new seeds annually [4].
GM Issues and Concerns
Issue
Concern
•Alteration of the plants nutritional
value.
A plants basic nutritional value could either be
increased or decreased till it is compositionally
distinct from its non-GM equivalent. This could
result in over-consumption of a particular
nutrient [5, 11].
•Production of allergenic foods
Using genes fromcrops, which are known to
cause an allergic reaction, e.g. peanuts, could
create allergenic crops. These would be
undetectable till consumed by a susceptible
person [5].
•Scientists arrogance
Some scientists are arrogant in their assumptions
as to GM crop safety. Such as Professor Derek
Burke, chair of advisory committee on novel
foods who stated, “GM Soya doesn’t require
testing. If people don’t believe us they should
avoid the foods” [8].
•Unintended interactions (possible
toxin production).
Possible production of undesired products as a
result of gene or gene product interactions.
Scientists don’t know yet know the whole
genome of most crops [12].
Conclusions
Interest and concern over the Genetic
Modification of crops is an issue that
refuses to go away and is never likely to.
Any technique that harnesses science in
such a way as GM does is always going to
attract attention from scientists,
consumers and the media alike.
The consumer no longer wants to be told
that everything is OK, if it clearly isn’t,
as was the case in the UK BSE crisis.
Regardless of whether or not people
believe him, Pusztai’s work has raised
some serious questions as to the safety of
GM crops [8].
Consumers are concerned about the safety
of GM foods, but who do they believe
when scientists and the people developing
these techniques can’t even agree?
The method of testing GM crops is based
on substantial equivalence. If the GM
crop is substantially equivalent to its nonGM counterpart it is classed as safe.
People refuse to be misled anymore. The
public are now demanding to know what
is present in their foods. This can only be
brought about by the publication of more
scientific safety trials, (Pusztai’s trials
were the first in the UK on the effect of
GM crops in mammals), allowing the
consumer to decide for themselves
whether or not GM foods are safe to eat.
The main public concerns are with health and
safety. Selective use of evidence by both
scientists and the media has led to a high level
of consumer mistrust. Liam Donaldson, Chief
medical officer of England states, “There is no
current evidence to suggest that the GM
technologies used to produce food are
inherently harmful. However, nothing can be
absolutely certain in a field of rapid scientific
and technological development” [9].
References
[1]
Reiss, M.J. and Straughan, R. (1996) Improving nature? The Science and
Ethics of Genetic Engineering. Cambridge University Press. pp33-63.
[2]
The Royal Society (September 1998) Genetically modified plants for food
use. pp1-22.
[3]
The Lancet (1999) Health risks of genetically modified foods. The Lancet
353, 1811.
[4]
Polkinghorne, J.C. (2000) Ethical issues in Biotechnology. TibTech 18, 8-10.
[5]
Uzogara, S.G. (2000) The impact of genetic modification of human foods in
the 21st century: A review. Biotechnology Advances 18, 179-206.
[6]
Gibbs, D. (2000) Globalisation, the bioscience industry and local
environmental responses. Global Environmental Change 10, 245-257.
[7]
Tortora, J. G., Funke, B.R. and Case, C.L. (2001) Microbiology, an
Introduction, 7th edition. Benjamin Cummins USA. pp248-269.
[8]
Despatches. Investigation into the safety of GM foods. 11-03-99.
[9]
Horton, R. (1999) Genetically modified foods: “absurd” concern or welcome
dialogue? The Lancet, 354, 1314-1315.
[10]
Chiter, A., Forbes, J.M. and Blair, G.E. (2000) DNA stability in plant tissues:
implications for the possible transfer of genes from GM food. FEBS Letters,
481, 164-168.
[11]
Kuiper, H.A. et al (2002) Safety aspects of novel foods. Food Research International, 35,
267-271.
[12]
Moseley, B.E.B. (1999) The safety and social acceptance of novel foods. International
Journal of Food Microbiology, 50, 25-31.