Download GMO answerkey

Group Activities Associated with the News
Story
1. Now, after having read the newspaper article, go back and note
anything that you believe is in error or that you find questionable
regarding facts that are stated as established truth.
Possible errors that students should note:
•
Statement made by Patricia Crowley regarding genetically
modified corn being the cause of the allergic reaction is
speculative since she didn’t have all of the information needed to
make a comment about the corn used in the taco.
• Switching around the genes from insects and bacteria is
incorrect; bacterial genes were placed in the transgenic corn, one
of which produced a protein lethal to certain insects. Genes from
insects are not being placed in plants although studies in
“designing” insects, that is transgenic insects, are being
conducted.
• Statement that “it’s a wonder we’re not all dead from people
playing around with our food” is not a scientifically objective
statement; it is inflammatory and not based on evidence.
• Super Maize corn does not have introduced genes to make it
resistant to disease; diseases result from bacterial, fungal, or
viral infections, not insect attack.
• Super Maize corn does not have genes from a fungus inserted
into its genome, but rather from bacteria.
• Super Maize was not shown to be a potentially serious allergen to
young children or people with compromised immune systems and
was not banned by EPA for use in human food for that reason. It
should be emphasized in the case that GMOs have not been
shown to pose a health threat to humans or animals.
Note: The errors present in the newspaper article are pointed out in
the letter to the editor that is part of the case study.
2. Prepare a list of questions concerning genetically modified
organisms (dealing with the science involved, not legal questions) that
you would like to have answered.
The questions that will be generated by the student groups will differ
widely and will have to be addressed individually after they are
submitted.
Research Questions for Student Groups
The answers provided for each of the questions below are abbreviated.
Students who develop PowerPoint presentations are expected to
provide further details.
1. Provide a brief overview of recombinant DNA technology. What are
restriction enzymes? What are plasmids?
The short answer is genes from different organisms are recombined
into a single molecule. It is produced in the lab by cutting DNA from
different organisms with restriction endonucleases (restriction
enzymes) so that the DNA has “matching” ends. The different DNA
molecules are then brought together and the molecules ligated
together using DNA ligase. Plasmids are circular DNA molecules
present in bacteria that are self-replicating and which can “carry” a
number of other genes, including genes obtained from another
organism. The plasmids replicate along with the bacteria when grown
in culture and can thus be used to produce large quantities of
recombinant DNA in a relatively short period of time. Plasmids can also
be used as vectors to deliver a gene into a cell; they make good
vectors because they are more stable than linear DNA fragments.
The following websites shown below give more details about the
process.
•
Wikipedia discussion: http://en.wikipedia.org/wiki/
Recombinant_DNA
• Restriction enzymes: http://www.accessexcellence.org/AE/AEC/
CC/restriction.html
• Plasmids, recombinant DNA, restriction enzymes: http://
www.life.uiuc.edu/molbio/background/background.html
2. Who are Stanley Cohen and Herbert Boyer and what was their role
in the development of recombinant DNA technology? What was the
Asilomar conference on recombinant DNA? What was the conclusion of
the conference?
Boyer’s work in the early 1970s focused on the activity of a class of
enzymes called restriction endonucleases that targeted particular
sequences of nucleotides and cut DNA molecules at these sites. His
belief was that such molecules would have “sticky ends” that could be
joined to other DNA molecules having similar ends. He needed some
way to introduce recombined molecules into living cells to determine if
they would be propagated and how they would behave.
Cohen was investigating the behavior of plasmids that could carry
genes from one bacterium to another. He and his coworkers had
developed techniques to introduce plasmids into bacterial cells.
In 1972, Boyer and Cohen decided to collaborate. Boyer would modify
Cohen’s plasmids and then Cohen would introduce the modified
plasmids into bacterial cells where the altered genetic material could
be propagated. The potential uses of such methodology were quickly
recognized by the scientific community.
The Asilomar conference was held in 1975. It was organized by
scientists working in the field of molecular biology and recombinant
DNA. Some 140 participants—mostly biologists, but a few lawyers,
physicians, and reporters—gathered to consider the possible
ramifications of the “new technology” of genetic manipulation. Could
such experiments lead to the creation of dangerous new organisms?
Such concerns led these scientists to call for a voluntary moratorium
on certain types of recombinant DNA experiments and to propose
guidelines to address safety issues. The guidelines called for use of
disabled bacteria for recombinant DNA experiments until potential
hazards could be adequately evaluated.
3. What is Agrobacterium tumefacians? What is the role of this
organism in production of transgenic plants? What are some current
and potential applications of transgenic plants?
A. tumefacians is a Gram negative, soil-borne bacterium that causes
crown-gall disease in plants. It contains a Ti-plasmid (tumor-inducing
plasmid), which is normally involved in the infection of wounded plants
and transfer of the bacterial plasmid DNA into the plant genome. Once
the T-DNA becomes integrated into the plant chromosome it ensures
the proliferation of the bacterial DNA and leads to the formation of the
tumor. By removing the Ti portion of the plasmid and inserting other
genes (foreign DNA), one can create transgenic plants. Following the
gene insertion, the plant tissues are transferred to a selective medium.
Only those plants expressing the selectable marker gene survive, and
it is assumed also possess the transgene of interest. By use of tissue
culture techniques, one can regenerate whole plants, which are then
allowed to produce seed. The progeny of these plants are evaluated,
with the desired result being plants that reproduce with the inserted
foreign gene and which express the foreign gene in their tissues.
Potential and actual applications of genetically modified plants and
animals include:
•
•
•
•
•
•
•
use in basic research;
herbicide-resistant plants;
flavor-enhanced foods;
foods that keep longer;
insect-resistant plants;
a source of organs for xenotransplantation;
improved animal traits for food production (e.g., more lean
muscle mass, more milk production);
• for vaccine production;
• for vaccine testing;
• for toxicity testing;
• production of therapeutic proteins; and
• as disease models.
The following webpage from BMJ.com was used as a source for the
above information on the applications of GMOs: http://www.bmj.com/
cgi/content/full/318/7183/581.
Current applications of transgenic plants include insect and herbicide
resistant plants. Future uses include using plants as agents for vaccine
delivery.
The following websites give more information on transgenic plants.
•
•
Soil and Crop Sciences at Colorado State University. What are
transgenic plants? http://cls.casa.colostate.edu/TransgenicCrops/
what.html
European Initiative for Biotechnology Education. Transgenic
plants. http://www.ipn.uni-kiel.de/eibe/ENGLISH/U9.HTM
•
U.S. Food and Drug Administration. Methods for genetically
engineering a plant. http://www.fda.gov/fdac/features/2000/
biochart.html
4. Certain government agencies play a role in regulation of the
production of genetically modified plants. What are the roles of the
EPA (Environmental Protection Agency), FDA (Food and Drug
Administration), USDA (U.S. Department of Agriculture), and APHIS
(Animal and Plant Health Inspection Service) in permitting the
development and growth of transgenic plants?
There are four government agencies that have some role in regulation
of transgenic plants. Perhaps the most interesting discovery that
students will make is that the FDA does not regulate genetically
modified foods. Companies producing GMOs cooperate with the FDA on
a strictly voluntary basis. All genetically engineered foods and feed
crops go through the FDA for a consultation, but the FDA does not
formally approve the product as being safe.
The USDA’s role comes through the agency of APHIS, the Animal and
Plant Health Inspection Service. APHIS is responsible for regulating the
introduction of genetically engineered organisms. It is charged with
imposing appropriate confinement measures to ensure isolation of
GMOs from other plants that could be negatively affected by them.
The EPA is a player in permitting genetically engineered plants because
of its role in regulating the environmental and human health impacts
of pesticides; Bt corn contains a gene to kill certain types of insect
pests. This role falls under the EPA due to section 408 of the Federal
Food, Drug, and Cosmetic Act.
See the web pages below for additional information on the Federal
Food, Drug, and Cosmetic Act and government oversight agencies:
•
•
U.S. Food and Drug Administration. Federal Food, Drug, and
Cosmetic Act. http://www.fda.gov/opacom/laws/fdcact/
fdctoc.htm
In particular, see Chapter IV—Food. http://www.fda.gov/opacom/
laws/fdcact/fdcact4.htm
United States Department of Agriculture, Animal and Plant Health
Inspection Service. http://www.aphis.usda.gov/
•
U.S. Food and Drug Administration. Are bioengineered foods
safe? http://www.fda.gov/fdac/features/2000/100_bio.html
• U.S. Regulatory Agencies Unified Biotechnology Website. http://
usbiotechreg.nbii.gov/
5. What is Bt protein? How does it act on insects? Why is it considered
“safe” for ingestion by humans and animals?
Bt is an endotoxin naturally produced by the bacterium Bacillus
thuringiensis that acts selectively on the larval stage of Lepidopteran
insects, the principal stage in the life cycle causing damage to plants
through feeding. The protein is selective and generally does not harm
insects in other orders such as bees, beetles, flies, etc. It is considered
safe for humans—the acidic environment of our stomach quickly
denatures the protein and prevents it from remaining active.
The Bt protein binds to the wall of the gut of Lepidopteran caterpillars
and the insect stops feeding almost immediately. The wall of the gut
soon breaks down and bacteria present in the caterpillar invade the
body cavity of the insect, causing death of the insect larva through
septicemia.
6. What is an ELISA? Compare a direct versus a sandwich ELISA.
Provide examples of things an ELISA procedure can be used to detect.
How can an ELISA be used in identifying Bt corn?
ELISA stands for enzyme linked immunosorbent assay. It is a
technique for identifying if particular antigens or antibodies are present
in blood sera, bodily fluids, or other materials (such as Bt protein in
corn). The easiest way to understand an ELISA is to see a picture of it
—shown in the following URL from Biochemistry, 5th ed. by Jeremy M.
Berg et al.: http://www.ncbi.nlm.nih.gov/books/bv.fcgi?
rid=stryer.figgrp.515
There are several types of ELISA procedures; the most common are
the indirect (used to determine serum antibody concentrations) and
sandwich (used to detect serum antigen).
If the Bt protein is present in corn, it can be detected using an ELISA
since it is effectively an antigen that will produce antibodies specific to
it when it is injected into an animal. These antibodies produced by
animals injected with the Bt protein can then be used for detection
purposes as part of an ELISA system.
7. What is Bacillus thuringiensis? How is it related to other species of
bacteria? Talk about the microbiology of this bacterium. Do the same
for Streptomyces hygroscopicus.
B. thuringiensis is a soil-dwelling, aerobic, bacillus-shaped bacterium
that produces endospores. It is closely related to B. cereus and B.
anthracis, differing mostly in the plasmids that they possess. B.
thuringiensis causes a disease of Lepidopteran caterpillars and is used
as a biopesticide sold under the trade names of Dipel and Thuricide. It
is considered to be a safe biological control of certain insect pests.
Strain differences exist, some of which attack the larval forms of
insects other than Lepidopterans. The species is taxonomically placed
in the phylum Firmicutes, a phylum also containing genera such as
Clostridium, Staphylococcus, Streptococcus, and Lactobacillus.
S. hygroscopicus is an aerobic soil microbe that produces several
different types of antibiotics. It is a member of the phylum
Actinobacteria, which contains genera such as Corynebacterium,
Mycobacterium, Propionibacterium, and Bifidobacterium. There is a
gene in S. hygroscopicus that produces the enzyme phosphinothricin
acetyltransferase. When this gene is inserted into the genome of a
plant, it makes the plant tolerant to herbicides containing the active
ingredient glufosinate.
Useful URLs for information on these bacteria include:
•
Colorado State University Cooperative Extension. Bacillus
thuringiensis. http://www.ext.colostate.edu/PUBS/insect/
05556.html
• Health Canada. Insect-resistant and glufosinate-tolerant maize
(corn), DBT418. http://www.hc-sc.gc.ca/fn-an/gmf-agm/appro/
34bg_dekalb-ct_dekalb_e.html
8. What is an allergen? What are the most common food allergies?
Give an overview of the typical reaction(s) to a food allergen by
humans. What is anaphylactic shock? How can an allergen lead to
development of anaphylactic shock?
An allergen is any substance that elicits an allergic reaction when it is
recognized by the immune system. Allergens are thus antigens.
The most common food allergies are nuts, seafood, eggs, legumes,
soy, milk, wheat, sesame, and corn. There is no inclusive list of
allergens, but a list of common allergens can be found at the following
website maintained by the International Union of Immunological
Societies (IUIS) Allergen Nomenclature Sub-committee: http://
www.allergen.org/Allergen.aspx.
A food allergy, like other allergic reactions, is an exaggerated immune
response. It is triggered by exposure to a food that is generally
harmless to people. Reactions may range from mild to fatal. The cause
of food allergies is not completely understood, but involves antibody
and histamine production in response to a specific food. Symptoms
may involve the oral area, lips, tongue, throat, or be confined mainly
to the stomach and intestines. They may involve other body parts after
the food is digested and absorbed. Symptoms usually occur within a
few minutes to several hours after eating; rarely the symptoms may
appear some hours after food ingestion. If it is an oral allergy,
symptoms usually consist of itching lips, tongue, and throat, and
sometimes swollen lips. Such allergies do not normally result in
anaphylactic shock. Food allergies may also lead to hives, hoarse
voice, and wheezing. Occasionally individuals may experience low
blood pressure and blocked airways. The only effective treatment for
food allergies is to avoid the offending food.
Anaphylaxis is a severe, whole-body allergic reaction that occurs
suddenly and can be fatal. Release of histamines and other substances
from tissues in different parts of the body leads to airway constriction,
gastrointestinal symptoms such as abdominal pain, cramps, vomiting,
etc., and a lowering of blood pressure due to vasodilation which leads
to shock, hives and angioedema (hives on lips, eyelids, throat, and/or
tongue) that can block the airway. If prolonged, anaphylaxis can cause
heart arrhythmias.
Anaphylaxis can occur in response to any allergen including food.
Though anaphylaxis is seen infrequently, it is life-threatening and can
occur at any time once someone has been exposed to the allergen.
Useful pages from MedlinePlus, Health Information from the National
Library of Medicine:
•
Allergen: http://www.nlm.nih.gov/medlineplus/ency/article/
002229.htm
•
Food allergy: http://www.nlm.nih.gov/medlineplus/ency/article/
000817.htm
• Anaphylaxis: http://www.nlm.nih.gov/medlineplus/ency/article/
000844.htm
9. “Genetically modified organisms do contain genes obtained from
other species, but the procedures used to produce these GMOs are
closely regulated by companies, universities, the state and federal
government, and scientists themselves.” This statement is from the
letter written to the editor of the newspaper. How “closely” are GMOs
regulated? What are the procedures used by companies, universities,
and scientists to regulate production and distribution of GMOs?
Compare these to those by state and federal agencies (see Question 4
above).
I personally find this an interesting question and one that would be
worthwhile investigating further, but it is not a question that I would
readily assign in the class. Simply put, this question will potentially
have very different answers depending on the companies and
universities that are investigated. Scientists may have personal views
that come into play in their individual research that may differ from
the procedures outlined by the university or company for which they
work. One should expect diverse answers to this question.
Some useful websites to guide the students in addressing this question
are listed below. The guidelines from governmental agencies can be
found using the resources given in the answer to Question 4.
Useful sites:
•
•
•
•
National Academy of Sciences. Executive summary—Genetically
modified pest-protected plants: Science and regulation. http://
nap.edu/execsumm_pdf/9795.pdf
GMO Food For Thought. Missouri considers ban on local
regulations for genetically modified crops. http://
www.gmofoodforthought.com/2006/03/
missouri_considers_ban_on_loca.htm
Transgenic Crops: An Introduction and Resource Guide. The
regulatory process for transgenic crops in the US. http://
cls.casa.colostate.edu/TransgenicCrops/evaluation.html
Videos of Cornell Conference on Agricultural Biotechnology.
http://www.nysaes.cornell.edu/comm/gmo/conference.html
10. Consider the economic and health benefits of GMOs, both realized
and potential. At what point would current and potential future
benefits outweigh the risks? Relate the development of GMOs to other
historical developments in biology that were “controversial” at the time
(e.g., vaccination) and current “controversial” developments (e.g.,
embryonic stem cells).
This is another interesting question, but one that is broad in its scope.
I do not assign it in most classes. When I do, I have different student
groups examine one “controversial” topic and present their findings to
the class. In addition, one could invite an economist to talk to the class
about cost/benefit analysis and then have the class discuss the issue
of GMOs and compare this controversial issue to some other biological
“controversy.”
11. Genetically modified animals as well as plants have been
produced. Give an overview of the techniques for producing transgenic
animals. What are some of the potential applications of genetically
modified animals?
Genetically modified animals can be produced in a variety of ways. A
common technique involves injection of hundreds of copies of the
foreign gene (the transgene of interest) into a fertilized egg cell prior
to its initiation of mitosis. The egg is then implanted, with hopes that
some of the eggs will acquire the transgene and produce individuals
carrying the transgene that is expressed in them. The following URLs
provide information on a variety of techniques used to genetically
modify animals.
•
Animal and plant transformation—Application of transgenic
organisms in agriculture: http://www.ag.uiuc.edu/~vista/
html_pubs/irspsm91/transfor.html
• Transgenic animals: http://www.ucalgary.ca/~browder/
transgenic.html
Potential and actual applications of genetically modified plants and
animals include:
•
•
•
•
use in basic research;
herbicide-resistant plants;
flavor-enhanced foods;
foods that keep longer;
•
•
•
insect resistant plants;
a source of organs for xenotransplantation;
improved animal traits for food production (e.g., more lean
muscle mass, more milk production);
• for vaccine production;
• for vaccine testing;
• for toxicity testing;
• production of therapeutic proteins; and
• as disease models.
The following webpage from BMJ.com was used as a source for the
above information on the applications of GMOs: http://www.bmj.com/
cgi/content/full/318/7183/581
The following webpage from Altweb, The Alternatives to Animal Testing
Web Site, is useful for answering this question: http://
altweb.jhsph.edu/publications/ECVAM/ecvam28.htm
12. If someone is particularly interested in the legal aspects of GMOs
then the following might be appropriate questions to consider as part
of a presentation. Why did the lawyers for the Linder family choose to
pursue a civil rather than a criminal case? Consider levels of evidence
required in civil versus criminal cases to obtain a decision of guilt or
innocence. Should criminal charges be considered in this case? What is
criminal negligence?
Civil suits can be brought by individuals against other individuals.
Criminal cases require that the state file charges and mounts a
prosecution of the individuals. Criminal suits require a higher level of
proof in order to gain a guilty verdict than do civil cases. For example,
a criminal case requires presentation of evidence that the individual/s
is/are guilty beyond reasonable doubt, a level of certainty that says
that there is no reasonable alternative possible; a civil case requires a
preponderance of the evidence, which implies that the evidence more
than likely is adequate to establish a particular point. Beyond
reasonable doubt is the highest level of proof that has to be met in a
trial.
For a legal definition of criminal negligence, see the relevant entry
from Answers.com at http://www.answers.com/topic/criminalnegligence. Basically, criminal negligence involves a failure on the part
of someone or some organization to use reasonable care to avoid
consequences that would threaten or harm the public’s safety. It also
implies that the individual or organization could have foreseen such an
outcome and failed to act to prevent the harm from occurring.
There is no evidence that criminal negligence occurred in this
hypothetical case of the death of the Linder child. Wrongful death
provides an avenue for legal action on the part of the family of
someone who dies if it is believed that the death was caused by the
wrongful act or negligence of another. Such cases are handled
independently of any criminal negligence cases—someone found not
guilty of criminal negligence might still be found responsible in a
wrongful death suit and have to pay damages.
13. Have transgenic insects been produced? What technique was used
to develop them? For what purpose(s) were they produced?
Yes, transgenic insects have been produced, e.g., silk worms, pink
bollworm, mosquitoes, and the New World screwworm.
The technique used for development of transgenic insects is the
insertion of the “foreign DNA” of interest into a mobile element, a
transposon or “jumping gene.” For example, transgenic strains of the
New World screwworm are generated by microinjecting embryos with
piggyback (a mobile element) that is part of a vector plasmid. The
plasmid with the mobile element is much more likely to recombine
with the host chromosome and insert the foreign DNA into the host
genome.
Much of the initial work is designed to replace the use of sterile insect
technique (SIT) programs with transgenic insects. Sterile insects
produced by SIT tend to have low fitness in wild populations and thus
large numbers have to be released into the wild in an effort to reduce
successful reproduction of native populations of the insect. One of the
goals of creating transgenic insects is to produce populations that are
sterile, but have good fitness in the wild and thus would be more
effective at mating with wild populations and reducing the reproductive
potential of that insect. Efforts are also underway to produce
mosquitoes incapable of transmitting malaria, honeybees that are
resistant to parasites and diseases, silkworms to produce
pharmaceutical and industrial proteins, and kissing bugs unable to
transmit Chagas disease.
14. How can genes from a genetically modified plant be transferred to
a plant that is not genetically modified? Can such gene transfers occur
between different species of plants? What are the dangers, if any, for
harm to non-pest organisms feeding on the GMO or coming in contact
with the pollen of the genetically modified plant? Are there dangers of
transferring genes from a genetically modified plant to a “weed”
species growing nearby? Why would such an event be of concern?
The simplest way for such a transfer to occur would be via crossfertilization: pollen from the genetically modified (GM) plant would
pollinate a non-GM plant and lead to the formation of a viable zygote
that would carry the transgene and now be in the “wild” population.
There are reports of gene transfer from GM plants to non-GM plants
growing in the vicinity.
There is debate as to whether genes from GM rape were transferred to
a distantly related plant called charlock (a weed species) and this
hybrid then produced viable seed. Some reports indicate that an
herbicide-resistant charlock was present in the area where GM rape
was being grown. Other researchers believe that the frequency of such
an event in the field is very low and such an event has never been
detected in previous assessments of GM plants.
A laboratory study in 1999 showed that pollen from Bt corn caused
high mortality rates in monarch butterfly caterpillars. The fear was that
pollen from the corn could land on milkweed plants, the normal food
source for monarchs, and cause the death of the caterpillars. The
study was not conducted under natural field conditions however and so
has to be viewed in that light.
There is concern about the possibility of horizontal gene transfer also.
This concerns the transfer of genes from the GM plant to bacteria
living in the soil. The concern is that engineered DNA is released by
the plant as cells die and the free DNA is then available to be acquired
by bacteria in the process of transformation. Antibiotic resistance
genes acquired in this way by bacteria could then be transferred to
other species of bacteria by various gene exchange mechanisms and
lead to the spread of antibiotic resistant genes in the bacterial
populations.
There are issues of concern for the environment as addressed here,
but there is no indication that any of these have led to environmental
damage. Concerns include: the GMO escapes and introduces
engineered genes into wild populations; the engineered gene persists
after harvesting; the reduction in the spectrum of plants, resulting in a
loss of biodiversity; an increased use of chemicals in agriculture to
take advantage of the GM plants. See the following:
•
Smalla, Kornelia, et al. 2000. Horizontal transfer of antibiotic
resistance genes from transgenic plants to bacteria—Are there
new data to fuel the debate? http://www.agbios.com/docroot/
articles/2000246-A.pdf
• Whitman, Deborah. 2000. Genetically modified foods: Harmful or
helpful? http://www.csa.com/discoveryguides/gmfood/
overview.php
15. What methods are available for detection of genetically modified
crops and products? Which is most sensitive? Which has the broadest
application in GMO detection and is generally accepted for regulatory
purposes? Why? What is the advantage(s) of using an immunoassay,
ELISA? Which is faster and more readily available for use in “field”
sampling?
The analytical methods used are DNA based, protein based, or
phenotype based. The methods used are PCR (for DNA detection),
immunoassay (for protein detection), or bioassays (for phenotype
characterization).
PCR has the broadest application for use in regulatory evaluation. It is
very sensitive and with proper selection of primers can distinguish one
molecule of DNA in a complex DNA mixture. It is highly selective. The
disadvantages of PCR include: DNA is generally not detectable in
highly heat-processed foods (unless one uses real time PCR, which
requires very expensive lab equipment and thus limits its widespread
adoption), it results in false positives because of its sensitivity, it is
time consuming (normally 3–5 days processing time), and the cost is
relatively high ($100–$300 per sample).
ELISA relies on a reaction between antibodies and the foreign inserted
protein. The reaction between the antibodies and antigen is detected
by a color change that can be measured quantitatively. ELISA is less
sensitive than PCR and it is necessary to validate its usefulness with
each food type before it is routinely used. The results are typically
available in minutes and the cost is quite low ($2–$10 per sample).
Immunoassays cannot distinguish between different sources of
biotechnology-derived recombinant DNA. Proteins may also be
denatured when foods are processed and so the method is more useful
for raw foods or food ingredients that have undergone minimal
processing.
See: Tripathi, Leena, 2005. Techniques for detecting genetically
modified crops and products. African Journal of Biotechnology 4(13):
1472–1479.