Flash
-- KRAFT:
GE Foods Experiment For The Holidays
Scientists
Fear 'Uncertainty' Of Genetically Altered Animals
Genetically
Modified Outcome
Genetically
Modified Genes
Found In Human Gut
First
GM Insects To Be Released
Seeds
of Secrecy
GM
Crops Threat To Organic Farming
A
Tomato Fish Or A Fish Tomato?
'Frankenfish'
Spawn Controversy Debate Over Genetically Altered Salmon
Biotech: The Basics
by
Rachel Massey
Genetic
engineering is the process by which genes are altered and transferred
artificially from one organism to another. Genes, which are made
of DNA, contain the instructions according to which cells produce
proteins; proteins in turn form the basis for most of a cell's
functions. Genetic engineering makes it possible to mix genetic
material between organisms that could never breed with each other.
It allows people to take genes from one species, such as a flounder,
and insert them into another species, such as a tomato -- thus,
for example, creating a tomato that has some of the characteristics
of a fish.
Starting in the 1980s and accelerating rapidly in the past decade,
companies have begun using genetic engineering to insert foreign
genes into many crops, including important foods such as corn
and soybeans.[1] Just in the past few years, genetically engineered
ingredients have begun appearing in many foods in U.S. supermarkets;
they have been detected in processed foods such as infant formulas,
drink mixes, and taco shells, to name a few examples.[2] These
foods are not labeled, so consumers have no way to know when they
are eating genetically engineered food.
Genetic engineering is an extremely powerful technology whose
mechanisms are not fully understood even by those who do the basic
scientific work. In this series, we will review the main problems
that have been identified with genetically engineered crops.[3]
Most genetically engineered crops planted worldwide are designed
either to survive exposure to certain herbicides or to kill certain
insects. Herbicide tolerant crops accounted for 71% of the acreage
planted with genetically engineered crops in 1998 and 1999, and
crops designed to kill insects (or designed both to kill insects
AND to withstand herbicides) accounted for most of the remaining
acreage. A small proportion (under 1%) of genetically engineered
crops planted in 1998 and 1999 were designed to resist infection
by certain viruses.[4]
Genetically engineered herbicide-tolerant crops are able to survive
applications of herbicides that would ordinarily kill them. The
U.S. food supply currently includes products made from genetically
engineered herbicide-tolerant crops including "Roundup Ready"
canola, corn, and soybeans which are engineered to withstand applications
of Monsanto's Roundup (active ingredient, glyphosate), as well
as crops engineered to survive exposure to other herbicides.[1]
Genetically engineered pest-resistant (or pesticidal) crops are
toxic to insects that eat them. For example, corn can be engineered
to kill the European corn borer, an insect in the order lepidoptera
(the category that includes butterflies and moths). This is accomplished
by adding genetic material derived from a soil bacterium, BACILLUS
THURINGIENSIS (Bt), to the genetic code of the corn. BACILLUS
THURINGIENSIS naturally produces a protein toxic to some insects,
and organic farmers sometimes spray Bt on their crops as a natural
pesticide. In genetically engineered "Bt corn," every cell of
the corn plant produces the toxin ordinarily found only in the
bacterium.
Unfortunately, genetically engineered crops can have adverse effects
on human health and on ecosystems. And by failing to test or regulate
genetically engineered crops adequately, the U.S. government has
allowed corporations to introduce unfamiliar substances into our
food supply without any systematic safety checks.
Here are some of the reasons why we might not want to eat genetically
engineered crops:
** Ordinary, familiar foods can become allergenic through the
addition of foreign genes.
Genetic engineering can introduce a known or unknown allergen
into a food that previously did not contain it. For example, a
soybean engineered to contain genes from a brazil nut was found
to produce allergic reactions in blood serum of individuals with
nut allergies. (See REHN #638.) Allergic reactions to nuts can
be serious and even fatal. Researchers were able to identify the
danger in this particular case because nut allergies are common
and it was possible to conduct proper tests on blood serum from
allergic individuals. In other cases, testing for allergenic potential
can be much more difficult. When genetic engineering causes a
familiar food to start producing a substance previously not present
in the human food supply, it is impossible to know who may have
an allergic reaction.
** Genetic engineering has the potential to make ordinary, familiar
foods become toxic.
In some cases, new characteristics introduced intentionally may
create toxicity. The Bt toxin as it appears in the bacteria that
produce it naturally is considered relatively safe for humans.
In these bacteria, the toxin exists in a "protoxin" form, which
becomes dangerous to insects only after it has been shortened,
or "activated," in the insect's digestive system. In contrast,
some genetically engineered Bt crops produce the toxin in its
activated form, which previously only appeared inside the digestive
systems of certain insects.[5] Humans have little experience with
exposure to this form of the toxin. Furthermore, in the past humans
have had no opportunity or reason to ingest any form of the Bt
toxin in large quantities. When the Bt toxin is incorporated into
our common foods, we are exposed each time we eat those foods.[6,
pgs. 64-65.] And of course, a pesticide engineered into every
cell of a food source cannot simply be washed off before a meal.
Toxicity can also result from characteristics introduced unintentionally.
For example, a plant that ordinarily produces high amounts of
a toxin in its leaves and low amounts in its fruit could unexpectedly
begin to concentrate the toxin in its fruit after addition of
a new gene. (See REHN #696.)
Unpleasant surprises of this sort can result from our ignorance
about exactly how a foreign gene has been incorporated into the
engineered cell. Foreign genes can be added to cells by various
methods; among other options, they can be blasted into cells using
a "gene gun," or a virus or bacterium can be used to carry them
into the target cells.[7] The "genetic engineer" who sets this
process in motion does not actually control where the new genes
end up in the genetic code of the target organism. The "engineer"
essentially inserts the genes at a random, unknown location in
the cell's existing DNA. These newly-inserted genes may sometimes
end up in the middle of existing genetic instructions, and may
disrupt those instructions.
A foreign gene could, for example, be inserted in the middle of
an existing gene that instructs a plant to shut off production
of a toxin in its fruit. The foreign gene could disrupt the functioning
of this existing gene, causing the plant to produce abnormal levels
of the toxin in its fruit. This phenomenon is known as "insertional
mutagenesis" -- unpredictable changes resulting from the position
in which a new gene is inserted.[8] Genetic engineering can also
introduce unexpected new toxicity in food through a well-known
phenomenon known as pleiotropy, in which one gene affects multiple
characteristics of an organism. (See REHN #685.)
** Genetically engineered crops can indirectly promote the development
of antibiotic resistance, making it difficult or impossible to
treat common human diseases.
Whatever method is used to introduce foreign genes into a target
cell, it only works some of the time, so the "genetic engineer"
needs a way to identify those cells that have successfully taken
up the foreign genes. One way to identify these cells is to attach
a gene for antibiotic resistance to the gene intended for insertion.
After attempting to introduce the foreign genes, the "engineer"
can treat the mass of cells with an antibiotic. Only those cells
that have incorporated the new genes survive, because they are
now resistant to antibiotics.
From these surviving cells, a new plant is generated. Each cell
of this plant contains the newly introduced genes, including the
gene for antibiotic resistance. Once in the food chain, in some
cases these genes could be taken up by and incorporated into the
genetic material of bacteria living in human or animal digestive
systems. A 1999 study published in APPLIED AND ENVIRONMENTAL MICROBIOLOGY
found evidence supporting the view that bacteria in the human
mouth could potentially take up antibiotic resistance genes released
from food.[9] Antibiotic resistance among disease-causing bacteria
is already a major threat to public health; due to the excessive
use of antibiotics in medical treatment and in agriculture, we
are losing the ability to treat life-threatening diseases such
as pneumonia, tuberculosis, and salmonella.[10] (See REHN #402.)
By putting antibiotic resistance genes into our food, we may be
increasing the public health problem even further.
The British Medical Association, the leading association of doctors
in Britain, urged an end to the use of antibiotic resistance genes
in genetically engineered crops in a 1999 report. "There should
be a ban on the use of antibiotic resistance marker genes in GM
[genetically modified] food, as the risk to human health from
antibiotic resistance developing in micro-organisms is one of
the major public health threats that will be faced in the 21st
Century. The risk that antibiotic resistance may be passed on
to bacteria affecting human beings, through marker genes in the
food chain, is one that cannot at present be ruled out," the Association
said.[11]
Continued. To Part 2 of 4
=====
*Rachel Massey
is a consultant to Environmental Research Foundation.
[1] Union of Concerned
Scientists, "Foods on the Market," available at http://www.ucsusa.org.
Choose "biotechnology" in the bar at the bottom of the screen,
then click on "Foods on the Market."
[2] Consumers Union,
"CONSUMER REPORTS: Genetically Engineered Foods in Your Shopping
Cart," Press Release, August 23, 1999. Available at http://www.consumersunion.org/food/gefny999.htm.
[3] For one recent
overview, see Environmental Media Services (EMS), REPORTERS' GUIDE:
GENETIC ENGINEERING IN AGRICULTURE, Edition 1 (October 2000),
available from EMS, Washington, D.C., (202) 463-6670 or at http://www.ems.org.
Also see Pesticide Action Network North America (PANNA), "Genetically
Engineered Crops and Foods: Online Presentation," available at
http://www.panna.org/panna/resources/geTutorial.html.
[4] Clive James,
"Global Review of Commercialized Transgenic Crops: 1999" ISAAA
BRIEFS No. 12: Preview, produced by International Service for
the Acquisition of Agri-Biotech Applications (ISAAA). Available
at http://www.isaaa.org/
Global%20Review%201999/briefs12cj.htm.
[5] See Michael
Hansen, "Potential Environmental and Human Health Problems Associated
with Genetically Engineered Food." Presentation delivered at CREA
International Seminar on Transgenic Products, Curitiba, Brazil,
October 11, 1999. Available from Consumer Policy Institute, Yonkers,
N.Y.: 914-378-2455.
[6] National Research
Council, GENETICALLY MODIFIED PEST-PROTECTED PLANTS: SCIENCE AND
REGULATION (Washington, D.C.: National Academy of Sciences, 2000).
ISBN 0309069300.
[7] Union of Concerned
Scientists, "Fact Sheet: Genetic Engineering Techniques." Available
at http://www.ucsusa.org. Choose "biotechnology" in the bar at
the bottom of the screen, then click on "Genetic Engineering Techniques."
[8] See Food and
Drug Administration, "Premarket Notice Concerning Bioengineered
Foods," FEDERAL REGISTER Vol. 66, No. 12 (January 18, 2001), pg.
4710.
[9] Derry K. Mercer
and others, "Fate of Free DNA and Transformation of the Oral Bacterium
STREPTOCOCCUS GORDONII DL1 by Plasmid DNA in Human Saliva," APPLIED
AND ENVIRONMENTAL MICROBIOLOGY Vol. 65, No. 1 (January 1999),
pgs. 6-10.
[10] See World Health
Organization (WHO), OVERCOMING ANTIMICROBIAL RESISTANCE (Geneva,
Switzerland: World Health Organization, 2000). Available at http://www.who.int/infectious-disease-report/2000/.
[11] British Medical
Association Board of Science and Education, "The Impact of Genetic
Modification on Agriculture, Food and Health -- An Interim Statement,"
May 1999. Summary statement available at http://www.bma.org.uk/public/science/genmod.htm.
Source:
Rachel.org
