Genetically Modified Crops
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Genetically modified crops are crops whose genetic coding has been artificially altered to give it a useful trait from either a different strain of the plant or from a different species entirely. For example, scientists can add a gene from bacteria to corn, giving the corn the ability to produce insecticides. By adding foreign genes, crops can be changed to withstand weed killers and insects, grow larger or faster, and become better adapted to their environment.

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Designing New Genes
The first step to modifying crops is determining the genes to alter. This is one of the most difficult steps as it requires determining not only what a gene does for the plant, but also how it interacts with the genes around it and how it is regulated as well.

Once the workings of a gene are understood, it is possible to design a new gene that will cause the desirable trait to appear in that crop. The gene is put into a plasmid along with other pieces of DNA. There are a number of pieces that must be included when a gene is to be added to the plant. First, a promotor sequence is chosen in order to ensure expression of the gene in the plant. The second piece is the transgene, which is the actual modified gene that encodes for the new trait. The final piece is a termination sequence that indicates the end of the gene. Sometimes, the plasmids contain a marker sequence. The marker sequence is usually a gene encoding herbicide or antibiotic resistance. Plants that adapt the plasmid into their genome will be resistant to the herbicide or antibiotic, and will survive when the herbicide or antibiotic is applied.

The transgene can convey several different traits to the crop. For instance, disease or pest resistance is common. Herbicide resistance can also be included into a genetically modified crop. Another use of genetically modified crops is to allow a plant to produce a product, like a vitamin, mineral, or pharmaceutical compound.

Some examples of genes that have been incorporated into crops.

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Adding the Gene
There are two common ways to to add the new genes to an organism: using a "Gene gun", or using an infectious bacteria.

The "Gene gun" is powered by air pressure, and loaded with gold particles that have been coated with the genetic material. The gold particles are fired at a Petri dish containing the plant cells. If a gold particle lands in the nucleus of a cell, the genes attach themselves to different chromosomes. Every gene attached to a different section of a chromosome is referred to as a different event. Different events can cause different results in cells because of how they are worked into the existing DNA.

Agrobacterium can also be used to insert a gene into the plant cells. The plasmid containing the transgenic gene is first inserted into the agrobacteria. The agrobacteria are allowed to infect the plant cells. The agrobacteria inserts the plasmid into the plant cell’s genome. The agrobacteria’s plasmids are deadly to the plant cell, but the transgenic plasmid will, hopefully, allow the plant to develop the desired trait.

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Checking for the Gene
Since the insertion is not always successful, the plant cells must be tested for incorporation of the new genetic material. This is done by applying a herbicide or antibiotic to the plant cells. Because the marker genes convey immunity to the herbicide or antibiotic, only cells that have adapted the new genetic material will survive the application. These cells will then be grown into full plants.

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Effects on Human Health
There are many concerns about the safety of genetically modified food. For instance, genetically modified foods could possibly cause an increase in allergies. Scientists are testing new crops to determine how allergenic the crops may be for human beings. Some genetically modified strains of corn have raised concern, and many scientists are questioning the allergenic nature of genetically modified crops.

Another concern is antibiotic resistance. If a genetically modified crop carries a gene for antibiotic resistance, there exists a possibility that this resistance could be given to harmful bacteria, making infections more difficult to fight using antibiotics. This is called horizontal transfer, because a trait (in this case, resistance to an antibiotic) transfers to another species. Horizontal transfer occurs in nature, and in the laboratory. In the human body, the most likely site for horizontal transfer occurring between bacteria and genetically modified food would be in the stomach. Some scientists claim that, due to the acidity of the stomach, horizontal transfer is unlikely to occur. The possibility of horizontal transfer is still a valid concern when considering the safety of genetically modified crops.

Antibiotic resistance genes may cause another problem in the human stomach. If a person consumes genetically modified food with the antibiotic resistance genes, then takes an antibiotic orally, the proteins created by the antibiotic resistant food may neutralize the effects of the antibiotic drug, therefore harming the person and allowing harmful bacteria to continue to infect the person.

There is also a concern about eating unnatural DNA. While humans consume non-human DNA often and without health problems, little is understood about the way in which DNA is digested. One of the promoters used, called the cauliflower mosaic virus promoter (CaMV), has raised concern because of the effect of the full virus on vegetables. While there have been no reports of health problems related to ingesting the CaMV promoter, a danger may still exist. The newly designed genes may cause problems, and research is being done on the digestion of DNA.

Genetically modified crops may also have different nutrient levels from natural crops. While industry studies show that genetically modified crops have very little nutrient changes, there has been evidence in soybeans that genetically altering the plant may change the nutrients. Soybeans produce isoflavones, which have been shown to help prevent heart disease and breast cancer. Genetically modified soybeans have slightly different isoflavones, that may affect their preventative benefits.

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Damage to the Natural Environment
Genetically modified crops may also have an impact on the environment. While some genetically modified crops are created with the intention of lessening the damage to the environment, it is possible that the genetically modified crops may be causing harm in other ways.

Proponents of genetically modified crops claim that pest resistance will lessen the need for pesticide spraying, which will ease some of the strain on the environment. The Bacillus thurgenesis toxins provide crops protection from ECB, but not from other pests. Even with genetically modified crops, there is a need to spray pesticides, even when other genes for resistance to other pests are included, one crop cannot resist all pests.

The ECB-killing proteins effect monarch butterfly larva, as well as other non-targeted moths and butterflies. Researchers reported in 1999 that when pollen from genetically modified corn was sprinkled on the milkweed leaves that were the food for the larva, they would eat less, grow more slowly, and had a 50% mortality rate than larva that ate leaves without pollen or with non-genetically engineered corn pollen.

Continued research into this problem showed that, while the pollen is deadly to the monarch and other butterflies and moths, the range that is effected by the pollen is not very large. Since corn produces pollen for only a short amount of time, some scientists claim that the effect on non-target species is negligible. Even so, the effects of such modifications on non-target species are still being studied to determine the true environmental impact of genetically modified crops,

Another concern of genetically modified crops is that they may pass the genes onto organic crops, weeds or similar native crops. This would represent contamination of the environment and organic food supply, and may prove deadly to either the plants, or organisms that feed on the plants. Similarly, resistance to antibiotics or herbicides could generate “super-organisms” that cannot be killed when needed. Since resistance genes are often used as marker genes, there is a possibility that these genes could be transferred to weeds or other plants.

It is also possible that the proteins created by the genetically modified crops will leak into the soil, and cause harmful effects on the microorganisms living near the plant’s roots. Scientists have not thoroughly studied the relationship between soil microorganisms and plant health, but this issue is now being addressed because of genetically modified crops.

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