• What biotech crops does DuPont currently market?
• What is horizontal gene transfer (HGT)?
• Does HGT happen regularly?
• What is the rate of HGT in nature?
• How can we account for the comparatively low rate of HGT?
• Can DNA move from biotech crops decaying in fields to soil microorganisms?
• Can genes from biotech-derived plants move from ingested food to the bacteria in our intestines?
• Can genes from biotech-derived plants move from ingested plant material into intestinal cells?
• Why do some biotech crops contain antibiotic resistance marker genes?
• Will the use of antibiotic resistance markers in biotech crops have detrimental effects on the environment or health by increasing microbial resistance to antibiotics?

DuPont currently markets herbicide and insect resistant (Bt) corn and herbicide tolerant soybeans and canola. These products, sold under the Pioneer® brand, provide farmers with new crop management options and increased productivity. Before marketed, these products were rigorously tested and reviewed by regulatory authorities for food safety, environmental impacts and product performance.

HGT is defined as the movement of genes between two independent organisms, in contrast to the transfer of genes from parent to offspring. It can occur between two very different species, two similar species or two individuals of the same species. HGT involves not only the movement of a new gene into a cell but also its long-term maintenance by the recipient cell.

Yes. HGT is most common among bacteria, which have three separate mechanisms for transferring genetic material: conjugation, transduction and transformation. HGT involving bacteria and higher organisms, such as plants and animals, also appears to occur, but it is so rare scientists have not been able to detect it under natural conditions.

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The rate of HGT is relatively low when compared to the numerous opportunities for it to occur. Certain bacteria species are able to transfer genes through a mechanism called conjugation. The mechanism, the most successful of three that exist in nature, involves direct physical contact between cells. Under simulated natural conditions, using bacteria in the same species, scientists estimate that only one bacterial cell in approximately 100 million to one billion cells will successfully cross conjugate. HGT involving higher organisms, which occurs significantly less often, is most likely to occur via transformation. Transformation is a much less effective HGT mechanism and involves the direct uptake of DNA from the environment.

Organisms have developed a number of mechanisms to prevent the uptake and incorporation of new genes through HGT. These include:

• Physical barriers such as cell membranes and cell walls.
• Chemical barriers such as enzymes excreted by cells into the environment to degrade DNA; while enzymes breakdown foreign DNA that slips through a cell's physical barriers.
• Genetic mechanisms that prevent uptake and incorporation of foreign DNA into a cell's genetic material
• Physiological barriers that allow bacteria to take-up DNA only under very specific conditions that occur infrequently.

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Although we assume it is possible for soil microbes to take up DNA, all experimental attempts to induce gene transfer from biotech crops to soil bacteria and fungi in non-laboratory conditions have been unsuccessful. These results confirm findings of extensive field studies that show no detectable amount of genes from biotech-derived plants in soil microbes during and after field tests of biotech crops. Some investigators, under laboratory conditions, have been able to stimulate the transfer of DNA from plants derived through biotechnology to soil microbes. This was done to calculate a maximum rate of HGT rates of transfer. Investigators found the rates to be detectable, but very low. Other investigators have been unable to demonstrate HGT from biotech crops to soil microbes even under optimal laboratory conditions.

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Although we are certain that cells lining the intestine take up small pieces of DNA, there is no evidence entire genes have been transferred from food to intestinal cells.

Antibiotic resistance genes, closely linked to the gene for the crop trait, allow scientists to determine which plant cells successfully took up and integrated the gene of interest. These cells are retained and carefully nurtured under special conditions that encourage the cells to develop into complete plants. Antibiotic resistance markers are useful tools in the early stages of biotech crop development, but they contribute nothing to the agronomic performance of the crop. In fact, if the antibiotic resistance gene is functional in the biotech crop, it may lead to a loss of crop productivity, as well as requiring additional tests to ensure food safety. These costs, in conjunction with questions some members of the public have about their use, are prompting companies to develop other markers for identifying cells with the trait of interest.

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No. A number of scientific organizations have studied this question at length and all have concluded there is no risk to human and animal health or the environment from HGT of those antibiotic resistance genes used in crops developed through biotechnology to microorganisms. They came to this conclusion not only because the amount of HGT that will occur between biotech plants and microbes is virtually non-existent, but, more importantly because the number of naturally occurring antibiotic resistant microbes is many orders of magnitude greater than the trivial amount that might be added through HGT.