DNA in GM food and feed.

• Author: Ho, Mae-Wan
• Position: Biodevastation

"DNA is DNA is DNA," said a proponent in a public debate in trying to convince the audience that there is no difference between genetically modified (GM) DNA and natural DNA. "DNA is taken up by cells because it is very nutritious!" "GM can happen in nature," said another proponent. "Mother Nature got there first."

So, why worry about GM contamination? Why bother setting contamination thresholds for food and feed? Why award patents for the GM DNA on grounds that it is an innovation? Why don't biotech companies accept liabilities if there's nothing to worry about?

As for GM happening in nature, so does death, but that doesn't justify murder. Radioactive decay happens in nature too, but concentrated and speeded up, it becomes an atom bomb

Biotech companies are bypassing the strict environmental safety assessment required for growing GM crops in Europe by applying to import GM produce for food and processing only.

Is GM food safe?

There is both scientific and anecdotal evidence indicating it may not be; many species of animals were adversely affected after being fed different species of GM plants with a variety of GM inserts, suggesting that the common hazard may reside in the GM process itself, or the GM DNA.

How reliably can GM DNA be detected?

DNA can readily be isolated and quantified in bulk. But the method routinely used for detecting small or trace amounts of GM DNA is the polymerase chain reaction (PCR). This copies and amplifies a specific DNA sequence based on short "primers strings" of DNA that match the two ends of the sequence to be amplified, and can therefore bind to the ends to "prime" the replication of the sequence through typically 30 or more cycles, until it can be identified after staining with a fluorescent dye.

There are many technical difficulties associated with PCR amplification. Because of the small amount of the sample routinely used for analysis, it may not be representative of the sample, especially if the sample is non-homogeneous, such as the intestinal contents of a large animal. The primers may fail to hybridize to the correct sequence. The PCR itself may fail because inhibitors are present. Usually, the sequence amplified is a small fraction of the length of the entire GM insert, and will therefore not detect any other GM fragment present. If the target sequence itself is fragmented or rearranged, the PCR will also fail. For all those reasons, PCR will almost always underestimate the amount of GM DNA present, and a negative finding cannot be taken as evidence that GM DNA is absent. Consequently, the level of contamination is almost invariably underestimated.

There is an urgent need to develop sensitive, standardized and validated quantitative PCR techniques to study the fate of GM DNA in food and feed. Regulatory authorities in Europe are already developing such techniques for...