What are GMOs and GM foods?
Genetic modification is a biological technique that effects alterations in the genetic machinery of all kinds of living organisms. GMO is defined as follows by WHO (World Health Organization): “Organisms (i.e. plants, animals or microorganisms) in which the genetic material (DNA) has been altered in a way that does not occur naturally by mating and/or natural recombination”. The definition seeks to distinguish the direct manipulation of genetic material from the millennial-old practice of improvement in the genetic stock of plants and animals by selective breeding. With DNA recombinant technology, genes from one organism can be transferred into another, usually unrelated, organism. “GM foods” refer to foods produced from genetically modified plants or animals. Triticale is a grain widely used in bread and pasta. It was developed the 19th century by crossing wheat with rye (a conventional, selective breeding approach).
History of GM foods
The genesis of DNA modification technology can be traced back to 1944, when scientists discovered that genetic material can be transferred between different species.. In 1954, Watson and Crick discovered the double-helix structure of DNA, and the “central dogma” –DNA transcribed to messenger RNA, translated to protein – was established. Nobel Laureate Marshall Nirenberg and others had deciphered the genetic code by 1963. In 1973, Cohen et al. developed DNA recombination technology, showing that genetically engineered DNA molecules can be transferred among different species. The history really begins with Charles Darwin’s notions of species variation and selection. The first genetically modified plants – antibiotic-resistant tobacco and petunias – were produced by three independent research groups in 1983 . Scientists in China first commercialized genetically modified tobacco in early 1990s. In 1994 the US market saw the first genetically modified species of tomato with the property of delayed ripening approved by the Food and Drug Administration (FDA).
Do we need GM foods?
Before starting discussing the merits and demerits of GM foods, it is important to set forth why there is such great effort to develop them. There are three major challenges we are facing that motivate our resort to the new technology for help.
Expansion of population
The current global human population is approximately 7.35 billion (United Nations Department of Economic and Social Affairs/Population Division World Population Prospects. an annual addition of 83 million people is expected. The estimated global population will be 8.5 billion in 2030, and 9.7 billion in 2050. The expansion of population is one of the major contributors to undernourishment around the world. In 2016, the U.N. Food and Agricultural Organization (FAO) reported that 795 million people in the world were undernourished, among which 780 million people in developing regions . Therefore the eradication of hunger should be a priority of policymaking.
Decrease in arable land
FAO predicted that the finite amount of arable land available for food production per person will decrease from the current 0.242 ha to 0.18 ha by 2050 . This problem confounds those of population growth and malnutrition. Yet our ability to bring additional acreage under cultivation seems limited.
Bottleneck of conventional and modern breeding
Conventional breeding relies on sexual crossing of one parental line with another parental line, in hopes of express- ing some desired property (e.g. disease resistance) . To select for the desired trait and to dilute irrelevant or undesired traits, breeders choose the best progeny and back-cross it to one of its parents (plant or animal). The process usually takes several years (depending on generational time, e.g. 10–15 years for wheat) before actual expression of the desired trait that can be assessed, and further expanded by conventional breeding to commercially useful numbers.
Generation of GM crops
Directly transfer DNA
The most widely used technique for delivering exogenous DNA is microparticle bombardment. The technique was devel- oped in the late 1980s by Sanford . Naked, engineered DNA is coated on gold or tungsten microparticles, which, in turn, are delivered at high velocity into targeted tissues, such as embryonic tissues from the seed or meristems, propelled by pres- surized helium. There are other ways to deliver DNA into plant cells, including electroporation (letting the negatively charged DNAmove down an electric potential gradient) into protoplasts, microinjection, chloroplast transformation, silicon-carbide sliv- ers, mesoporous silica nanoparticles, etc. .However, particle bombardment remains more effective at transferring large DNA fragments – even whole chromosomes – simultaneously .
Indirectly using bacterial vehicle
The use of Agrobacterium tumefaciens opened a new era for inserting exogenous genes into plant cells. The soil bacterium A. tumefaciens infects plants, forming a gall at the crown. The bacteria actually alter the genome of the plant, not only causing proliferation of the plant cells, but also enabling the plant to produce modified amino acids as a specialized food source for themselves.
Direct editing of genomic DNA
In 2012, the “CRISPR-Cas9” system was developed. It constitutes a revolutionary genome editing tool, and pro- vides another method to alter genes in various type of cells [17,18]. This technique dramatically increases the efficiency of genetic engineering, making the work with plants much easier.
Benefits of GM foods
Modification of the chemical composition in food
Improvement in food processing
Products for therapeutic purposes
Potential risks of GM foods
Health risks associated with GM foods–Three major health risks potentially associated with GM foods are: toxicity, allergenicity and genetic hazards. These arise from three potential sources, the inserted gene and their expressed proteins per se, secondary or pleiotropic effects of the products of gene expression, and the possible disruption of natural genes in the manipulated organism
Ecological risks associated with GM food-It seems in a few years, insects and weeds will respond to the human-made pressures in their habitats by evolv- ing ways to nullify our clever design of transgenic crops
Disruption of the food web–Another issue is the possibility that the insect-resistant plants might increase the number of minor pests while reducing the major type of pest
Resistance to antibiotics–Development of resistance to antibiotics is a scourge well known to medical science, and is traceable to the over-use of therapeutic antibiotics in medicine and agriculture.