GENETICALLY MODIFIED ORGANISM- GMO
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 [11]. 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 [13].
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)
[1]. 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 [14].
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. [15].However, particle
bombardment remains more effective at transferring large DNA fragments – even
whole chromosomes – simultaneously [16].
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
Agronomic
benefits
Economic
benefits
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.
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