What are Genetically Modified Foods?
Genetically modified (GM) foods are produced from genetically modified organisms (GMO) and a food that comprise one or multiple ingredients that are derived from GM plants or organism, is also considered a GM food.
Genetically modified organisms (GMO) refers to an organism in which the genetic material has been changed through modern biotechnology in a way that does not occur naturally by multiplication and, or natural recombination. (WHO, 2005)
Modern biotechnology means the application of,
a) in vitro nucleic acid techniques, including recombinant deoxyribonucleic acid (DNA) and the direct injection of nucleic acid into cells or organelles, or
b) the fusion of cells beyond the taxonomic family, that overcome natural physiological, reproductive or recombination barriers and that are not techniques used in traditional breeding and selection.Types of GM Foods
Genetically modified foods include medicines and vaccines, foods and food ingredients as well as feeds and fibers. Foods have been modified to make them resistant to insects and viruses and also to be herbicide- and insecticide-resistant. Crops that have been modified for these purposes include:
• Oilseed rape (Canola)
· tomatoes with increased vitamin content
· foods such as peanuts with reduced or no allergenicity
· potatoes with higher starch content which absorbs less oil in cooking
· wheat with increased levels of folic acid to prevent spina bifida
· wheat with increased fibre to reduce the risk of colon cancer
· tomatoes that can ripen on the vine for better taste, but with a longer shelf life
· rice with increased pro-vitamin A content to help combat blindness in rice- dependent developing countriesGenetic Modification of Plants
Using techniques of genetic modification, it is possible to produce plants that may have the following properties:
· Disease and pest resistance
· Greater yields
· Herbicide tolerance
· Modified protein and oil content
· Improved nutritional properties
· Improved flavour due to delayed ripening
· Resistance to environmental stress e.g. drought, salinity, or cold
· Production of pharmaceuticals and other chemical substances(Food Safety Authority of Ireland, 1999)How Are Plants Modified?
Transgenic crops are referred to having received a foreign segment of DNA or gene(s) from another organism. Recombinant DNA techniques are often being used to alter the genetic makeup of different organisms by combining different selected individual genes from a few organisms or by inserting valuable genes into plant genomes.
This process of introducing foreign DNA into a plant genome is called transformation and is conducted, mainly using two methods:
a) The more popular method for genetic engineering of crop plants is natural gene transfer via an Agrobacterium tumefaciens vector, a bacterium normally found in soils. Many species of crop plants are susceptible to A. tumefaciens, which causes “crown gall” disease when the DNA (T-DNA) is transferred onto the plants in nature. However, removing the disease-causing gene from this bacterium now allows the T-DNA to transport foreign genes into plants.
A. tumefaciens cells, carrying the various selected foreign genes are then incubated with cultured cells of the recipient crop plant and a transgenic crop is regenerated from this process.
However, not all transgenic crops will be successfully regenerated and there is a need to identify the modified genes using marker genes which are closely linked to the genetic material being transferred. These marker genes also usually provide resistance to antibiotics such as kanamycin or herbicides.
b) Particle bombardment is also used for transformation of crops such as cereals. This process involves the coating of DNA on metal particles such as gold, and shooting the particles into plant cells using a particle gun. A small amount of plant cells that are hit with the coated particles receive the genetic material from the transferred DNA and transgenic crops can be regenerated from these cells.
Similarly to A.tumefaciens cells, marker genes are used for selection purposes and are only required in the initial stage of crop transformation. Genetic Modification of Microorganisms
Genetically modified microorganisms contain genetic material that is artificially introduced and rearranged in an intentional and predetermined manner, which is unlikely to occur in nature.
Examples of genetically modified microorganisms include:
· bacteria that produce or enhance the amounts of novel and/or modified enzymes (e.g. rennet for cheese-making)
· bacteria that produce substances (peptides or proteins) with medical applications e.g. interferon for cancer treatment and insulin for diabetics
· viruses with medical applications e.g. disabled vaccinia virus which is used in gene therapy
· bacteria that can be used as live-vaccines
· bacteria that can clean up toxic compounds or protect plants from pests and frost(Food Safety Authority of Ireland, 1999)How Are Microorganisms Modified?
Selected genetic material is introduced into recipient microorganisms by recombinant DNA techniques. This genetic material may be integrated into the resident chromosomes of the cells or extrachromosomal structures like plasmids. The genetic information is then transferred through a process of replication, cell division and chromosomal segregation.
This can be achieved through the following procedures:
a) Electroporation - This method is the most popular technique used for transformation of many varieties of microorganisms because of its simplicity. It only requires a brief exposure to a high voltage electric field in order to introduce genetic material into a microorganism.
b) "Natural" transformation - Bacteria such as Bacillus subtilis, Streptococcus pneumoniae and Haemophilus influenzae have a natural capacity to take up DNA and this useful property is used to introduce recombinant DNA into the host’s genomes.
c) Transformation through artificial competence – This process includes the incubation of certain bacteria in certain salt solutions to result in pore formation, thus allowing the introduction of recombinant DNA.
Genes which are selected to undergo tranformation into a new transgenic food product usually has valuable properties or important traits beneficial to the host product, such as genes present with natural insect resistance or desred nutrients. Genetic engineering or biotechnology allows genetic material to be transferred between any organism, including between plants and animals. For example, the gene from a fish that lives in very cold seas has been inserted into a strawberry, allowing the fruit to be frost-tolerant and maintain its natural goodness. However, modified genes are used in the production of GM foods in an early stage of the food production chain and may not always be present in the end product.References
Food Safety Authority of Ireland, Ireland. (1999). Food Safety and Genetically Modified Foods. Retrieved July 16, 2007 from http://www.fsai.ie/publications/reports/gmfood_report.pdf
Food Safety Authority of Ireland, Ireland. (2004). Food Safety and Genetically Modified Foods. Retrieved July 16, 2007 from http://www.fsai.ie/publications/leaflets/GM_leaflet04.pdf
Food Safety Department; World Health Organisation, Switzerland. (2005). Modern food biotechnology, human health and development: an evidence-based study. Retrieved July 15, 2007 from http://www.who.int/foodsafety/publications/biotech/biotech_en.pdf