MAC Winter 2001 Newsletter
Genetic modification or genetic engineering is one technology within a broader science known as biotechnology. This biotechnology includes a collection of scientific techniques that are used to create, improve or modify plants, animals and microorganisms. The process can be carried out by intact organisms such as yeast or bacteria or by natural substances, such as enzymes from organisms. Some of these techniques date back hundreds of years.
The ancient Egyptians used yeast to make bread dough rise, and to ferment grape juice to produce wine. In the 1860s, Louis Pasteur improved the wholesomeness of milk by heating it to kill off harmful bacteria. The use of bacteria and molds to make cheese is also defined as biotechnology.
For centuries, crop and livestock breeders have used conventional techniques, such as selective breeding, cross pollination and natural mutations, to improve plants and animals for human benefit. They studied the characteristics of plants and animals that were easy to observe or measure, and made selections for better quality, higher yield, improved taste or pest and disease resistance. Most of these traits depend on the information contained in the DNA within genes, which is what is crossed when animals or plants are bred.
Techniques to analyze DNA, developed within the last twenty years, enable breeders to locate specific DNA chromosome regions that correspond to particular production traits. Breeders can now use these techniques to quickly and accurately choose superior individual plants or animals to breed, speeding the process of genetic improvement.
In the 1970s a new type of biotechnology, called genetic engineering, was developed, which allowed scientists to produce desired traits even more quickly and in a more predictable manner. This technique combined biochemistry and molecular biology and involved the modification of genes within an organism or the transfer of specific genes between organisms.
The location, timing and amount of gene expression can all be controlled by genetic modification. This may be achieved by the transfer of a gene from one organisms to another (transgenics) or by the modification of a gene within an organism.
In the genetic modification process, a specific gene with a desired trait is identified, isolated and removed from one organism. The gene is placed into a bacterial cell and reproduced. Then the copied gene is studied using molecular techniques to verify that the replicated gene carries the desired trait.
Once the gene is verified, it may be relocated into the DNA of another organism to replicate the desired trait, or it may be modified within the original organism to alter characteristics. The "genetically modified organism" then makes new substances or performs new functions based on its new DNA.
Genetic modification can improve the ability of an organism to do something it already does. An adjustment in the amino acid balance in a particular corn variety improves its storage ability. It can suppress or stop an organism from doing something it currently does. In the Flavrsvr® tomato, the gene that codes for the softening of the tomato is "turned off", so the tomato does not soften as quickly. Genetic modification can also be used to make an organism do something entirely new. Some bacteria and yeast have been modified to produce chymosin, an enzyme used to make cheese.
Genetically modified organisms are extensively researched and tested, and safety information is reviewed by regulatory agencies in countries where these products are grown or imported. Three agencies in the U.S., the USDA, EPA and FDA, are responsible for regulation and testing. The USDA is the lead agency regulating the safe field-testing of genetically-enhanced new plant varieties. In order to receive permission to test a new biotech plant, an applicant must provide information about the plant, including all new genes and gene products, their origin, the purpose of the test, how it will be conducted, and specific precautions to prevent the escape of pollen or plant parts from the field test site. Impact on the environment, on endangered or threatened species, and "non-target" species are also considered.
The EPA has authority over all new pesticides, including genetically-enhanced plants which produce their own protection against pests. In deciding whether to register a new product, the EPA considers human safety, impact on the environment, effectiveness on the targeted pest, and any effects on other "non-target" species, including endangered or threatened species.
Legal authority for food labeling rests with the FDA. Foods derived from biotechnology must be labeled only if they differ significantly from their conventional counterparts, for example, if their nutritional content or potential to cause allergic reactions is altered.
With approval of the USDA Animal, Plant Health Inspection Service, over five hundred field trials have been safely conducted since 1987. About forty new agricultural products have completed all of the regulatory requirements and have been approved for sale.
Because genetic modification provides the capability to alter the inherited characteristics of an organism in a manner never before possible, it is seen as presenting both great opportunities and great risks. This dichotomy has generated a much debate from scientists, politicians and the public.
It is believed that on-going research in genetic engineering can hold the key to solving some of the worlds most significant problems. New products are being developed that have the potential to combat human disease, promote human health, reduce hunger, produce higher yields of food, combat animal disease and protect the environment.
Biotechnology can combat human disease through the use of more effective drugs and vaccines. It has led to the production of insulin for diabetes, interferon for the treatment of cancer, clot-busting enzymes for heart attack, as well as medicines for Parkinson's Alzheimer's, Aids and Leukemia.
Biotechnology can promote health in humans through production of nutritionally rich foods, such as grains, vegetables and fruits that contain more proteins, vitamins and minerals and less fatty acids.
It is estimated that biotechnology could reduce hunger by increasing crop productivity in the developing world by as much as twenty five percent. It could also help to prevent the post harvest loss of foods and grains, thereby increasing the amount of useable food produced. Many biotech crops may be able to grow under tougher growing conditions, such as drought, changing weather and nutrient-depleted soil.
Biotechnology is producing higher yields through crops with built-in protection from destructive insects, specific viral or fungal diseases and herbicide tolerance that allow for effective weed control with fewer herbicide applications. Biofertilizers, including nitrogen-fixing bacteria and some fungi, have the potential to provide nutrients to crops directly or to enhance the availability of soil nutrients to plants.
New products have been developed from biotechnology to combat animal disease. These include a vaccine that protects animals in the wild against rabies and a vaccine for "shipping fever," the major killer of beef cattle in feed lots. Scientists are working to develop animal feeds that provide the nutritional requirements of livestock, or prevent or correct nutritional disorders.
By increasing the productivity of farmland now in use, biotechnology offers the potential to protect other areas of the environment, including rain forests and wetlands, from conversion to food production. Biotech crops can also help farmers protect the land and conserve natural resources through reduced irrigation and tillage that save topsoil from erosion, reduced fuel usage and less use of pesticides.
Many scientist and public citizens are concerned about potential long-term effects of genetically modification, which involves the crossing of species that do not occur in nature. Some of the majors concerns are: escaped resistance into the environment, increase pesticide usage, introduction of allergens and toxins to food, antibiotic resistance and changes in food quality.
There is a concern that genes transplanted into pesticide-resistant crops may be spread unintentionally, by bird, insect or wind, from target crops to related weed species, creating a new class of "superweeds." Recently a field of canola, genetically modified to be resistant to an herbicide, cross-pollinated with a related weed species, resulting in a new strain of weed which was also resistant to the herbicide.
Another fear is that pesticide-resistant crops will cause an increase in the use of pesticides, which will find their way into the food and water supply. The widespread use of crops such as corn modified to include Bt, a safe natural pesticide, may also result in the development of Bt resistance in insects.
Many plants already contain small amounts of toxins. The modifications of the genetic make-up of plants, presents possibilities of unforeseen enhancement of natural toxins or the development of new toxins. An additional fear is that the genetic modification of foods might transfer allergens from other foods.
Scientists are not sure what impact eating large quantities of food with added vaccines and vitamins will have on young children. They also warn that inserted genes could change a foods nutritional value and possibly crucial qualities, such as cancer-inhibiting abilities. They also fear that the process, used in some genetically modified products, of using antibiotic resistant bacteria as a gene marker, may add to increased antibiotic resistance and diminish the effectiveness of drugs.
One social issue poses the question of whether biotechnology will increase the prosperity gap, giving farmers in rich countries an unfair advantage over those in poorer countries. Additional issues ask if biotechnology may concentrate economic power with large multinational companies, erode rural communities and reduce biological diversity.
Combat Human Disease
Insulin, used in the treatment of diabetes, is the product of one of the first genetically enhanced organisms. Researchers found that they could generate a consistent, reliable and inexpensive source of insulin by inserting a human gene into the genetic code of a bacterium. Insulin has been produced this way since 1982.
Scientists are working on a banana that delivers the Hepatitis B vaccine orally. The cost could be less than ten cents a dose, and no medical personnel would be needed to administer the vaccine. Farmers could grow the vaccine right in their own communities, eliminating transportation and refrigeration problems.
Promote Human Health
As many as a hundred million children worldwide suffer from Vitamin A deficiency, a leading cause of blindness. Millions of women of childbearing age are iron deficient, placing their babies at risk of physical and mental retardation, premature birth and natal mortality. Scientists have developed a strain of "golden" rice that contains more iron and beta carotene, a precursor of Vitamin A. This dietary staple can be locally grown and will deliver the needed vitamins.
Scientists have also discovered a way to boost beta-carotene levels in canola, and are researching a more nutritious strain of cassava, the leading source of calories in Africa. Biotechnology may also make it possible to identify and remove known allergenic agents from foods.
In 1999, the world population reached six billion; it could top nine billion by 2050. The worlds supply of usable farmland is shrinking, while the growing population requires more land. According to the U.N., eight hundred million people worldwide are already chronically malnourished. Biotechnology alone won't solve the problems of hunger and malnutrition, but it can play an important role, by increasing crop yields and decreasing spoilage.
Increased Crop Yield
Since the 1920s, the corn borer has been a major insect pest of corn. It destroys approximately seven percent, or forty million tons, of the world's corn crop every year. In North American the cost of the damage is said to exceed one billion dollars annually.
In field corn, the damage caused by borer larvae (caterpillars) reduces yields, causing harvesting difficulties because of broken corn stalks.
Sweet corn growers have traditionally protected their crops from corn borer, and a similar pest called corn ear worm by spraying with insecticides. Depending on the severity of the infestation, a field may be sprayed several times during the growing season.
Through genetic engineering, scientists have transferred genes from the common soil bacterium Bacillus thuringiensis (Bt) which has been used for years as an organic pesticide, into some corn hybrids as a means to control the European corn borer. Because Bt provides protection for the corn plant, use of insecticides for corn borer control can be reduced or eliminated.
Virus-resistant squash and papayas have been produced, and research is under way on virus-resistant sweet potatoes and other crops. Biotechnology has been used to pinpoint genes that could help wheat and rice, major food staple, grow in areas that are now hostile to crops. An experimental potato hybrid contains genes to resist a virulent strain of the so-called "late blight."
Selective herbicides that affect only certain species or families of plants allow farmers to control a wide range of weeds with little risk to the crop. Researchers have developed genetically enhanced crops with resistance to non-selective herbicides, such as Roundup and Liberty, that kill almost all plants upon which they are sprayed. Previously non-selective herbicides could only be used before planting or after harvest or the crop would have been killed. These new herbicides are safer and less likely to leach into the ground water.
Chromosome: a structure found in the nucleus of cells. It contains DNA molecules tightly coiled around proteins, and is visible under the microscopes.
Gene: a small section of a chromosome. It controls (either singly or in coordination with other genes) the production of proteins. Some genes turn on and off other genes and are not involved in protein synthesis. Genes are found in all living organism.
DNA: Deoxyribonucleic acid is the molecule that makes up genes. It is found in all cells, usually in the nuclei, and is composed of six molecules: sugars, phosphates and four bases. The order in which these molecules are arranged determines the traits of a particular organism. DNA directs the growth, organization, development and function of cells, controlling the way characteristics, such as eye color, are passed on to the next generation. It is not visible under a microscope.
Proteins: are chains of amino acids. They perform the needed functions of living organisms. When a gene is "expressed", it is translated into protein.
A,C,G and T: Abbreviations for the chemical names of the individual components of DNA, adenine, cytosine, guanine and thymine. The order of these along a DNA chain is what controls cell functions.
Genotype: the DNA code that controls the characteristics of an organism
Phenotype: The visual measurable characteristics of an organism
Locus: the location of a gene on a chromosome
Genetic Modified Organism or transgenic: an organism that has been modified by genetic engineering to contain DNA from an external source.
The science of genetic modification, as it is currently practiced, is carefully researched and heavily regulated for safety. However, there is always the potential for unintended consequences. This debate offers an opportunity for students to study the many facets of the issue, going beyond the headlines to form their own conclusions. An April 1999 study by researchers at Cornell Univ. focused on the effect of Bt corn on the Monarch butterfly. This study has become popularized in the press.
The study was conducted because the larva of the monarch butterfly is a plant chewing caterpillar, similar to the European corn borer. The larva primarily lives on milkweed plants, that often grow near cornfields. In the laboratory study, the monarchs were fed milkweed dusted with pollen from a specific strain of Bt corn with the greatest potential to kill monarchs. The larvae were fed only this food. Some of the caterpillars that ate milkweed leaves dusted with Bt corn pollen died within four days. The surviving monarchs that ate Bt corn pollen were smaller and had smaller appetites than the control.
The researchers of the study caution against over-interpreting the results to conclude that Bt corn poses a serious threat to monarchs. The USDA says there are a number of reasons that the effect of on monarchs is likely small.
Field corn pollen is produced for only a short time. Corn pollen is heavy and is not blown far from the corn fields by the wind. Farmers control milkweed, the primary host, in and around their fields. Finally, it is not known whether monarch butterflies will choose to feed on milkweed plants with Bt pollen when given the opportunity to choose other plants. USDA and EPA scientists have had discussions with the studys researchers and scientists are currently conducting follow up studies.
- Research additional genetic modification issues with your students: Biotechnology and International Trade; World Hunger; Potential to Fight Disease; Antibiotic Resistance and Allergens and Toxins.
- Take students to a grocery store and look for items that have corn or soybeans in them. Since fifty percent of corn and seventy percent of soybeans are grown from genetically modified seed, how many foods did you find that may be genetically modified?
Genes can be dominant or recessive. Dominant genes are always expressed in offspring. Recessive genes are expressed in offspring, only if both parents contribute recessive genes. You are a farmer who raises cotton. Youve decided to cross two of your cotton plants, a pure homozygous blue plant (BB) and a pure recessive white plant (- -), hoping to grow a light blue "Acid Wash" style fiber for denim jeans. If you are successful, you will produce a cotton fiber that will reduce the need of acid in the production of jean fabric. Use the Punnet square on the right to show the type of offspring you should expect. Note: The white plant is designated (- -) because it lacks a gene for any color. A (bb) would represent a white gene.
What fraction of offspring produce white cotton? (- - )
What fraction of the off- spring will produce homozygous blue cotton? (BB)
What fraction of the offspring will be heterozygous? (B -)
If the parents produced 100 offspring, predict how many will be white?
If you find that blue cotton is only produced by (BB) genotypes. Is the production of light blue fiber successful?
Activity from "From Genes to Jeans" by California Foundation for Agriculture in the Classroom.
- 2500 BC Egyptians began to domesticate Geese to make larger, tastier birds.
- 1800 BC Wine, beer and leavened breads were produced using fermentation and microorganisms.
- 1860s AD Louis Pasteur developed pasteurization and defined microbiology. Gregor Mendel experimented with pea plants to learn that traits (genes) can be passed on through generations.
- 1930 Between 1930 and 1965, U.S. production of corn increased 600% due to a hybrid corn that became available in 1922.
- 1953 The code of DNA was discovered by James Watson and Francis Crick.
- 1970 Norman Borlaug became the first plant breeder to win a Nobel Prize for his work with Green Revolution wheat varieties, which produce a high yield.
- 1973 A gene, or a specific piece of DNA, was successfully relocated from one organism to another by Stanley Cohen and Herbert Boyer.
- 1980s A process known as Polymer Chain Reaction, which replicates DNA was discovered.
- 1982 Biotechnology was used to develop human insulin for diabetes treatment.
- 1983 Plants were first produced from modern biotechnology practices.
- 1990 Through biotechnology, an enzyme called chymosin was created to replace rennet, a mixture extracted from calves' stomachs used to coagulate milk for cheese production. Now used worldwide.
- 1994 The Flavrsvr® tomato, the first whole food enhanced through biotechnology, was first approved for U.S. grocery stores.
- 1995 Soybeans produced through biotechnology were first introduced on the market.
- 1997 18 biotechnology crop applications were fully accepted by the US government.
- 1999 "Golden" Rice rich in beta-carotene, a Vitamin A precursor, was developed by researchers. This rice can prevent blindness in children in developing countries.
From Council for Biotechnology Information Web Site.
Mass. Department of Agricultural Resources
251 Causeway Street Suite 500
Boston, MA 02114
(617) 626-1771 Fax: (617) 626-1850
Web Site: www.massdfa.org
University of Massachusetts
Department. of Entomology
University of Massachusetts
Amherst, MA 01003
William Coli (413) 545-1051
California Foundation for Agriculture in the Classroom
P.O. Box 15949
Sacramento, CA 95853
(800) 700-AITC Fax: (916) 561-5697
Web Site: www.cfaitc.org
- Three Lessons Plans on the web site
- Whered you Get those Genes
- From Genes to Jeans
- Genetic Engineering in Agriculture
National Council for Agricultural Education
1410 King Street, Suite 400
Alexandria, VA 22314
(800)772-0939 - Fax: (703)838-5888
- Biotechnology for Plants, Animals and the Environment.
USDA Agricultural Biotechnology http://www.aphis.usda.gov/biotechnology/
National Agriculture Day www.agday.org
- Animated Tour of a genetically modified organism
Council for Biotechnology Information www.whybiotech.com
Agricultural Groups Concerned About Resources and the Environment www.agcare.org
Council for Agricultural Science & Technology www.cast-science.org
USDA Economic Research Service www.ers.usda.gov/Topics
About network http://environment.about.com/newsissues/environment/
Information for this newsletter was taken from the sources listed above .
Mission: Massachusetts Agriculture ion the Classroom is a non-profit 501 (c) (3) educational organization with the mission to foster an awareness and learning in all areas related to the food and agriculture industries and the economic and social importance of agriculture to the state national and the world.