Genetically modified (GM) foods which include foreign genes inserted using different molecular techniques is a new field. Accepting and rejecting GM foods make a big controversy. Scientists believe that genetic modification can provide a lot of advantages to human being. However, there are a lot of concerns have been raised against GM foods. These concerns including that it can pose a risk to human health. Therefore, GM foods should undergo safety assessment and it should be labeled to ensure their safety.
Genetically modified (GM) foods are those which have foreign genes inserted into their DNA. Those genes are inserted using either biological delivery systems by using microorganisms that have the ability to transfer genes to plants e.g. Agrobacterium tumefaciens and Agrobacterium rhizogenes or physical delivery systems by using microprojectile-mediated transformation (Eede et al. 2004).
Accepting and rejecting GM foods make a big controversy nowadays. Most scientists believe that this technology can solve world problem of hunger by increase the quantity and quality of foods (Engel et al. 2002). Moreover, it can reduce using of insecticides which is environmentally not friendly. Expressing of δ endotoxins gene from Bacillus thuringiensis into plants confers insect resistant to the crops (Engel et al. 2002). This technology has been applied to canola, corn, cotton and potato. However, any new technology carry concerns of risks and it should undergo safety assessment to ensure its legality and safety. An increase on the level of anti- nutrients in the food can lead to health problems. Heat-stable anti-nutrients such as phytoestrogens, glucinins were found to cause infertility problems in sheep and cattle (Dona and Arvanitoyannis 2009). Another concern was the possibility that marker genes such as antibiotic resistance genes may be transferred horizontally to gut bacteria. Therefore, the antimicrobial therapy against these bacteria will be reduced (Dona and Arvanitoyannis 2009).
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GM foods should be safe to be consumed by animals or humans. Therefore, toxicological studies must be conducted and safety assessments should be carried out to ensure their safety (Cockburn 2002, Kleter and Kuiper 2002).
2) How desired genes are transferred to plant tissues:
Movement of genes is occurred naturally between closely related species by reproduction and between different species by horizon gene transfer (HGT).
Genetically modified food created by transferring a gene with a desired trait to the plant cell. This transformation can be successfully approaches using biological delivery systems or physical delivery systems.
In biological delivery systems, two species are used Agrobacterium tumefaciens and Agrobacterium rhizogenes which are responsible to cause crown gall disease and lead to form a tumor to the infected plants (Kelly et al. 2009). These species have a special large plasmid called tumor inducing plasmid (Ti plasmid) in case of Agrobacterium tumefaciens and Root inducing plasmid (Ri plasmid) in case of Agrobacterium rhizogenes (Eede et al. 2004). When bacteria infect the plant a piece of DNA plasmid called transfer DNA (T-DNA) is transferred to the infected plant and integrated to nucleus chromosome. T-DNA transfer process is occurred with the help of proteins encoded by genes (vir genes) on Ti plasmid (Eede et al. 2004). This special property of Ti and Ri plasmid encourage using them in biotechnology to create GM plants. The transfer DNA (T-DNA) is replaced with the gene of a desirable trait. However, Agrobacterium vector has some limitation including: reduced ability to transfer DNA to monocot cells. Also, it requires injury of plant tissues which may lead to entry of others bacteria (Kelly et al. 2009).
The physical delivery system is done by micro-projectile-mediated transformation. It involves shooting metal particles coated with DNA into plant tissue. The advantage of this technique is that it targets the DNA to the chromosome of plant cell. However, it includes damage to the plant tissue and low yield of stable transformation (Eede et al. 2004).
3) Benefits of genetically modified (GM) foods:
3.1 Herbicide tolerance
Weeds or herbs which are grown near the crop plants are not desirable. Therefore, herbs should be controlled using herbicides. However, these herbicides can be damage to the crop plants. Therefore, genetic modification technology can solve this problem. There are two ways to develop herbicide tolerance plant. The gene coding for an enzyme insensitive to herbicides can be introduced to crop plants or by introducing a gene for an enzyme that can detoxify the herbicide. This method has been applied and success in different plants such as soy bean (Engel et al. 2002).
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3.2 Improvement of nutritional value
Genetically modified technology can improve the quality of foods by improving their nutritional value. Omega three fatty acids are known to have health benefits. A study conducted by Rosenberg, 2002 shows that these fatty acids significantly lower coronary heart diseases risks. The effect of genetically modified salmon with omega three fatty acids on lowering heart diseases was evaluated (Lutter and Tucker 2003). The study estimates that the salmon will provides 8.2% of omega three for adults. The study concluded that GM salmon would reduce the heart diseases by 0.2%. Therefore, the death due to heart diseases in US will be reduced to a reasonable number (Lutter and Tucker 2003).
3.3 Resistance to viruses, fungi and bacteria
Plants usually invaded with microorganisms (e.g. fungi, bacteria) and viruses which lead to destroy the plant tissues and consequently farmers will lose their crops. GM technology can provide plants resistance to the viruses, fungi and bacteria infection. Plants resistance to viruses created by inserted viral coat proteins to plants. The presence of these proteins in infected plants prevents viral genome from being replicated. Another method is by introducing viral replicase genes to plants. Plants resistant to fungi are achieved by inserting GM-induced biosynthesis of phytoalexins into plant cells (Engel et al. 2002).
3.4 Insect resistance
GM technology can reduce using of insecticides to control insects that cause serious damages to crop plants. Plants can be genetically engineered to be resistance against insect infection. Bacillus thuringiensis which is produced δ endotoxins which is effective against insects has been exploited in this field (Lutter and Tucker 2003).
4) Concerns of genetically modified foods:
Accepting genetically modified foods makes a strong argument nowadays. A lot of concerns have been raised against consuming foods that have new genes.
Food allergy is an issue that should be taken in account whenever any new food products introduced either for animal or human consumption. Allergenicity is resulted from interaction between exposure of unwanted protein and immunoglobulin E (IgE). Genetically modified soy bean with a gene from Brazil nut to improve protein content of soy bean has been shown to cause fetal allergy to people who have allergic to Brazil nut (Bakshi 2003). According to Union of Concerned Scientists, transgenic crops with novel proteins from nonfood sources might cause risks to human. However, another study was conducted by (KIlIÄ“ and Akay 2008) on the effect of long consumption of transgenic corn on the rats that were fed through three generations. The corn was modified with Bt toxin to be resistance to insects. The rates that feed on those transgenic corns show no allergenicity.
4.2 Antibiotic Resistance
Usually GM foods involve antibiotics resistance genes as marker genes which are used as an indicator that the cells become incorporated with desirable genes. However, there are concerns that those marker genes might transferred to pathogenic bacteria in gastro-intestinal (GI) tract in mammals. Therefore, GI bacteria might become resistance to antibiotics. Some European countries refused Bt corn which contain ampicillin resistance gene because of concerns that this gene will be transferred to GI bacteria. So, the bacteria will be resistance to ampicillin as an antibiotic (Bakshi 2003). The optimum physical and chemical condition of transferring the marker genes to gut bacteria has been studied. Rubisco small subunit (Rubisco SS) gene which has similar size to trans-genes that present in GM plants was used in the experiment.DNA analysis and PCR amplification of Rubisco SS genes shows that trans- genes need high temperatures (above 95°C) and pressurized steam treatment to be fully degraded to a small fragment. So, it will not be transferred to gut bacteria (Chiter et al. 2000 ).
4.3 Production of Pesticides
A research has been found that genetically modified potatoes are poison to mammals. Those potatoes were modified to produce Galanthus nivalis agglutinin (GNA) molecule, which acts as a natural insecticide. It was founded that those potatoes cause damage to immune system and vital organs of rats (Pusztai, 1999).
However, another study was conducted to evaluate the effect of transgenic KMD1 rice expressing Cry1Ab protein from Bacillus thuringiensis on a 90-day feeding rats.
The study concluded that there were no observable effects on the feeding rats including body weight, blood sample and histological studies. Although, there were some variation in result but it was within a normal reference (Schr\oder et al. 2007).
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5) Safety assessment of GM foods
GM foods should undergo safety testing in order to ensure their safety for consumers. The safety assessment of GM foods follows comparative approach i.e. foods compared with non GM counterparts in order to identify the differences (AFSSA 2008). There are four steps in order to assess potential hazards of GM foods:
An array of techniques which includes literature searches, in vitro, in vivo and in silico toxicology
Estimation of protein expression/exposure levels, bioinformatics, field trials, animal feeding studies
Nutritional assessment (Cockburn 2002).
There are several tests can be used in order to test GM foods including: the 90 day rat feeding study. An experiment has been concluded that 90 day rat feeding study has the ability to detect the biological/toxicological effects of the new gene product in the GM food (Knudsen and Poulsen 2007).
Detection of genetically modified organisms (GMOs) was one of the major concerns against GM foods. There are several methods to detect GMOs in GM foods; polymerase chain reaction (PCR) is the main one. PCR based on DNA extraction, purification and identification of a transgenic element in a food sample (Deisingh and Badrie 2005). There are several products sailed in Europe countries some with labeling and some without such as cheese made using chymosin, tomatoes and manufactured foods containing soya and maize ingredients from GM plants (Moseley 2002). Moreover, It seems that Japan have a great accepting of GM products. There are several GM foods available in their markets e.g. herbicide tolerant soybean, cotton, and canola, and insect-resistant corn, cotton, and potatoes (Hino 2002).
Also, about 70% to 85% of foods that available on supermarket shelves contain one or more ingredients derived from GM crops (Harlander 2002).
Genetically modification of food is a big topic and still has controversy nowadays. Accepting of any new technology also depends on ethical view to this technology (Weale 2010).GM foods can solve a lot of problems such as hunger due to increase in the population. However still it can pose some risks to environment and to human. GM foods cannot be fully accepted. Every GM product should undergo safety assessment to insure high level of safety to consumers. Also, any product on the markets should be labeled if it is totally as a result of genetically modification or if it contains any ingredients that are genetically modified.