Andrew Sayer and Barry Twidale

April 2002

Genetically Modified CropsScience and Concerns

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. Some common plant pests. Aphids (top), Wire-Worm (middle) and Colorado Beetle (bottom).Fig 1. Source: www.uky.edu/Agriculture/Entomology/entfacts/veg/ef304.htm

Who’s involved ?The Major Players:

• Monsanto (US).

• 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].

The Products:• Flavr Savr Tomato, (slow ripening).

Sourcehttp://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].

Fig 2. The Flavr Savr Tomato

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 re-inserted 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

•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.

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.

Genetically Modified Potatoes.

SOURCE: Tortora, Funke and case, (2001). [7]

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.

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 self-produced 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.

http://www.naturalscience.com/ns/cover/cover8.html

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 his research methods.”

• The rats showed organ and brain damage as high as 15% compared to the healthy rats.

•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.

Protein Interaction Gene InteractionPusztais Concerns

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

Issue Concern

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.

•Cauliflower Mosaic Virus (CMV) Promoter

•Antibiotic resistance marker genes

•Cross Pollination

•Terminator genes

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 ConcernsIssue•Alteration of the plants nutritional value.

ConcernA 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].

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].

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].

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].

•Production of allergenic foods

•Scientists arrogance

•Unintended interactions (possible toxin production).

ConclusionsInterest 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.

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?

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 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].

The method of testing GM crops is based on substantial equivalence. If the GM crop is substantially equivalent to its non-GM counterpart it is classed as safe.

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.