Genetically modified organisms
The availability of
genetically altered foods continues to be a hotly debated issue with
powerful lobbies on both sides. Corn that resists attacks by insects, canola
that is tolerant of herbicides, and cheese that can be made without using
animal rennet have been some of the advances introduced by genetic
modification, but some people worry that possible long-term effects may not
have been adequately assessed.
For centuries, food growers have tampered with plant and animal genetics
by crossbreeding in order to bring out desirable traits while suppressing
less desirable ones. The refinement of such techniques has enabled farmers
to produce increasingly abundant crops.
In recent years, food biotechnology has added a new dimension, thanks to
genetic modification. Genetically modified (GM) foods or genetically
modified organisms (GMOs) are terms that refer to a change in the code or
organization of the genetic material of an organism. One method to achieve
this change is "genetic engineering" – the practice of moving one gene or
group o genes from one organism to another.
The production of GMOs is regulated in the United States and Canada. To
date, each country has approved at least 40 plant varieties derived by
genetic modification. Soybeans, corn, and canola are the most widely
produced GM crops and furnish a number of ingredients that are used in
highly processed foods. In fact, about 70 percent of processed foods contain
at least some GM ingredients.
Improving on nature
Genetic engineering enables research botanists to add desirable
hereditary traits to almost any plant. Possibilities include producing more
nutritious foods; for example, corn with increased high-quality protein, or
a type of rapeseed that synthesizes more of the unsaturated fatty acids of
Agricultural scientists are also trying to alter plants to make them more
productive or more able to withstand adverse growing conditions, such as
drought. this type of genetic engineering has tremendous potential in
overcoming world food shortages; conceivably, arid desert areas may one day
produce drought-resistant grains.
Another approach involves engineering plants to be resistant to disease,
herbicides, and pests. One modification alters a plant's taste to make it
less attractive to insects, allowing farmers to reduce pesticide use.
Another is aimed at developing a plant resistant to new kinds of
herbicides that do not harm the crops and beneficial insects.
Cheese producers have also benefited from genetic modification. The
classic way to make cheese involves using rennet extracted from calf
stomachs to curdle milk. But chymosin, the major enzyme in rennet can also
be produced through genetic engineering. The bit of DNA, the gene, that
gives the instructions for the formation of chymosin has been isolated from
calf cells and copied, or "cloned." Inserting this gene into the genetic
machinery of certain bacteria (Escherichia coli), yeasts (Kluyveromyces
lactis), or fungi (Aspergillus niger) causes them to dutifully
churn out pure chymosin. Approved in 1990 by the Food and Drug
Administration in the United States, chymosin became the first product of
genetic engineering in our food supply. It is 100 percent identical to that
found in calf stomach, but because it does not come from animals, it is
acceptable to consumers who do not want meat products in their cheese.
Extraordinary precautions were taken before chymosin, made by recombinant
DNA technology, was marketed. Regulators ensured that no toxins of any kind
had been introduced and that no live recombinant organisms were present.
Cheese made with it is completely indistinguishable from that produced with
animal rennet. In any case, chymosin itself is degraded ruing cheese making
and none is left in the finished product. today, In North America, more than
80 percent of cheese is made using chymosin.
Despite the benefits of genetic modification, some people are concerned
that this type of manipulation may create adverse consequences.
Gene transfer to nontarget species. For instance, scientists will
often incorporate an antibiotic-resistant gene (or tracer) into the genetic
material that is being introduced into a plant. If the modified cell is able
to survive antibiotic treatment, it means that it has become resistant to
that antibiotic and has probably taken on other characteristics carried in
the newly added genetic material. So far, evidence that antibiotic-resistant
tracers can be transferred to a nontarget species such as a disease-causing
microorganism is sketchy, but theoretically, it could happen.
Reduced effectiveness of pesticides and herbicides. There is some concern
that insects will become resistant to the pesticides produced by crops that
have been genetically modified to produce their own pesticides, or that the
herbicide resistance of a GM crop will be transferred to a weed Another
concern is that these crops may harm beneficial insects along with the
intended crop-damaging pests.
Unintended harm to the organism or other organisms. Comparatively,
animals subjected to genetic engineering do not fare as well as plants. For
example, sheep injected with genetically engineered hormones to increase
wool growth become more vulnerable to the heat. Pigs and chickens treated
with special growth hormones develop painful bone and joint problems.
Also, there are ethical issues involved in tampering with animal genes.
Allergic reactions. Concern has been raised that allergens may be
transferred through genetic modification. This is unlikely to occur because
the structures of proteins introduced by genetic modification are compared
with extensive data bases of the structures of known allergens.
It's a question of benefits versus risks
The potential benefits of genetic modification are numerous. Sweet potato
is an important crop in Africa but is very susceptible to feathery mottle
virus. Inserting a set of genes from chrysanthemums that code for naturally
insecticidal compounds called pyrethrins has the potential of creasing
yields dramatically. the use of pesticides on cotton has already been
dramatically reduced by incorporating a gene that protects it from insects.
While there are environmental concerns about pollen drift and crossbreeding
with non-GM plants, there has not been a single adverse health effect.