Genetic modification (GM) is a contentious issue and some opponents believe that GM will damage the clean environment.
GM provides a way of expressing desirable characteristics in an organism that otherwise would not display them. It is the insertion of a gene into an organism, altering the genetic makeup. This produces a transgenic organism, one that expresses a foreign gene.
In animals, a gene is inserted into an embryo, modifying the genome to manufacture the product of this new gene. In plants, a gene is injected into a single cell that is grown from a seed into a plant. This plant expresses the new gene in all its cells.
What is the difference between GM and selective breeding?
Selective breeding is a form of genetic modification that doesn’t involve the addition of any foreign genetic material (DNA) into the organism. Rather, it is the conscious selection for desirable traits.
Pro-GM campaigners argue that humans have been ‘genetically modifying’ organisms for thousands of years, albeit without knowing that the favorable traits they were selecting for were determined by genes.
For example, humans have always selected cows with the highest milk yield and bred from these to produce herds with good milk production.
A chance mutant grape with no seeds was bred to produce seedless grapes now available in our shops and supermarkets.
Why are organisms genetically modified?
In plants, GM is used to enhance productivity by making crops more resistant to herbicides and pests, thereby increasing the yield of the crops. It can also be used to increase the quality of crops and fortify them with extra nutrients.
Transgenic animals are produced in science to aid the production of human therapeutics. Animals are also genetically modified to give them human diseases in order to test new drugs or to study the biology of disease, or to make them more ‘environmentally friendly’.
So far, animals that have been genetically modified have not been used for human consumption. The Animal Welfare Act states that approval for these techniques only is granted if the likely benefits of the research “are not outweighed by the likely harm to the animals”, and any research involving animals is strictly regulated.
Since the dawn of agriculture, humans have taken steps to improve plant traits, such as hardiness, taste, adaptability, and beauty. Thousands of years ago, farmers simply saved seeds from their best plants for replanting.
Over time, plant breeders developed increasingly sophisticated techniques to attain specific traits. The latest technique is genetic engineering (GE), and advocates say it’s just the next step in humanity’s long history of innovations for improving crop plants.
Detractors insist that there is a fundamental and dangerous difference between conventionally bred and genetically engineered plants.
What sets genetic engineering apart from all other types of crop improvements is that it involves transferring genetic material from one organism into the genetic material of a completely unrelated organism, DNA from bacteria into corn, for example. This doesn’t happen in other plant-breeding techniques.
Did you know that more than 70 percent of packaged foods sold in the U.S. contain ingredients derived from genetically modified organisms (GMOs)?
If a product label lists anything that is corn-, canola- or soy-based, such as corn syrup, cornstarch, or soy lecithin, you can be pretty sure it’s from a GMO.
However, according to the 2010 poll, when consumers were asked, “As far as you know, are there any foods produced through biotechnology in the supermarket now?” 8% said “no” and 64% said, “don’t know.” That’s because manufacturers aren’t required to label foods containing GMOs.
For both advocates and detractors to have a meaningful debate about genetic engineering, it’s helpful to understand the evolution of plant-breeding techniques.
What Are The Natural Ways Of SELECTING?
Traditionally, farmers saved seeds from plants with favorable traits, such as high yield or better flavor, for replanting. In doing so year after year, the farmers created new strains of crops. Farmers in other regions did the same thing, resulting in different strains suited to their needs.
The next development in plant breeding was cross-pollination, which involves intentionally transferring the pollen of a flower from one plant to the stigma of a flower from another plant of the same or closely related species. Successful pollination results in viable seeds.
When the seeds grow, with luck, one or more of the offspring plants will exhibit beneficial traits. It’s a painstaking process because trait inheritance isn’t a straightforward process of crossing a disease-resistant corn variety with an extra-flavorful corn variety doesn’t mean you’ll get offspring with both traits.
Cross-pollination requires the parent plants to be compatible that is, the same species or a closely related species. It’s still an important breeding technique and it’s the primary way amateur plant breeders create new varieties.
Hybridization
Cross-pollination can produce haphazard results, so plant breeders looked for ways to ensure more consistent offspring from crossed plants, resulting in a technique called hybridization.
The first step in creating a hybrid is to create two pure strains of plants by repeatedly inbreeding plants until a very stable strain is attained. Breeders then cross-pollinate these parent plants, yielding seeds that grow into uniform plants with predictable traits, called F1 hybrids. The drawback is that seeds from F1 hybrids won’t produce offspring with the same traits as their parents.
That’s why gardeners who save seeds for replanting usually avoid saving seeds from hybrids, and farmers who grow hybrids must purchase fresh seed each year. Similar to conventional cross-pollination, the creation of F1 hybrids is limited to compatible plants, usually the same or very closely related species. The tomato variety Early Girl is an example of an F1 hybrid.
Natural mutations can also create unique plants. When something causes a spontaneous disruption of the normal inheritance process perhaps a “mistake” in DNA replication of the offspring (or even just a portion of the parent plant) can display different characteristics. If the mutation confers some benefit that makes the plant better able to survive, the trait may be passed down to subsequent generations.
On rare occasions these mutations yield traits that are considered desirable to plant breeders. For example, the Red Bartlett pear is a mutation of the green-fruited pear; it tastes similar but has beautiful rosy red skin. Many variegated plants are the result of naturally occurring mutations that caught the eye of a breeder, who propagated plants from the mutated plant material.
Observing how mutations can alter offspring, plant breeders began trying to induce mutations using irradiation and chemicals, hoping they’d eventually stumble upon mutations that resulted in beneficial changes. Star Ruby grapefruit and Ice Cube lettuce are examples of varieties created by induced mutations.
Breeders also discovered that plants grown using tissue culture, during which plant tissue is cultivated using artificial nutrients in sterile conditions, are more prone to mutation than conventionally grown plants. Although the mutations are artificially induced, the DNA remains that of a single species.
In the early 1980s scientists created the first genetically modified organisms (GMOs) by inserting genetic material from one organism into the DNA of a completely unrelated organism, even a non-plant species. This breakthrough is the only method available to plant breeders to confer beneficial traits between unrelated species.
To create “Bt corn,” for example, scientists incorporated genetic material from Bacillus thuringiensis (a bacteria that produces a substance toxic to caterpillars) into the DNA of corn plants. The result? Corn plants that resist corn earworm and corn borer, so the crops require fewer pesticide applications.
The next wave of genetically modified plants includes the “Roundup-Ready” crops. Scientists insert DNA from a soil bacterium to makes the crops tolerant of Roundup herbicide. Farmers can spray the herbicide to kill weeds without damaging the resistant crop plants.
Developers of genetically modified crops defend their work, citing reduced pesticide use and improved yields. Genetic modification has also produced plants with higher nutrient levels than their conventionally bred counterparts.
Although genetic modification has been around for almost three decades and the U.S. Food and Drug Administration has deemed GMOs safe, many consumers still balk at the idea of mixing the genes of entirely different organisms. Wary consumers talk of “Frankenfoods” and express concern about hidden allergens and other undiscovered biological effects. Organic growers worry that the pests will develop resistance to Bt, an important organic insecticide.
Environmentalists and farmers fear the creation of “superweeds” when pollen from herbicide-tolerant crops is inadvertently transferred to wild plants. And farmers who grow non-GM crops under organic certification or for export into countries that ban GM foods worry that genetic drift will contaminate their non-GM plantings. Crazy, paranoid ramblings? Maybe not.
Twenty-one species of weeds now show resistance to Round-Up and thus require the application of stronger herbicides.
Canada learned the hard way that it can be almost impossible to segregate genetically modified and non-GM crops and widespread contamination from GM canola has eliminated organic canola in most areas of Canada.
Bt-resistant bollworms were found in cotton fields in Mississippi and Arkansas within seven years of the introduction of Bt cotton.
What’s Next?
The first genetically modified food animal, AquAdvantage(R) salmon, is awaiting government approval. If it’s approved, it would be the first genetically altered animal approved for human consumption in the U.S. Down the road.
Genetically modified plants could be used to produce pharmaceuticals. In the meantime, scientists continue to look to genetic engineering to improve crops, for example, make them higher-yielding, more nutritious, and have more resistance to drought and pests.
Advantageous outcomes of these genetic modifications include increased food production, reliability, and yields; enhanced taste and nutritional value; and decreased losses due to various biotic and abiotic stresses, such as fungal and bacterial pathogens.
These objectives continue to motivate modern breeders and food scientists, who have designed newer genetic modification methods for identifying, selecting, and analyzing individual organisms that possess genetically enhanced features.
For plant species, it can take up to 12 years to develop, evaluate, and release a new variety of crop in accordance with international requirements, which specify that any new variety must meet at least three criteria: it must be genetically distinct from all other varieties, it must be genetically uniform through the population, and it must be genetically stable.
While advances in modification methods hold the potential for reducing the time it takes to bring new foods to the marketplace, an important benefit of a long evaluation period is that it provides opportunities for greater assurance that deleterious features will be identified and potentially harmful new varieties can be eliminated before commercial release.
The easiest method of plant genetic modification used by our nomadic ancestors and continuing today is a simple selection. That is, a genetically heterogeneous population of plants is inspected, and “superior” individuals plants with the most desired traits, such as improved palatability and yield are selected for continued propagation. The others are eaten or discarded.
The seeds from the superior plants are sown to produce a new generation of plants, all or most of which will carry and express the desired traits. Over a period of several years, these plants or their seeds are saved and replanted, which increases the population of superior plants and shifts the genetic population so that it is dominated by the superior genotype. This very old method of breeding has been enhanced with modern technology.
An example of modern methods of simple selection is marker-assisted selection, which uses molecular analysis to detect plants likely to express desired features, such as disease resistance to one or more specific pathogens in a population. Successfully applying marker-assisted selection allows a faster, more efficient mechanism for identifying candidate individuals that may have “superior traits.”
Superior traits are those considered beneficial to humans, as well as to domesticated animals that consume a plant-based diet and they are not necessarily beneficial to the plant in an ecological or evolutionary context. Often traits considered beneficial to breeders are detrimental to the plant or animal from the standpoint of environmental fitness.
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