Scrambling and gambling with the genome.

• Author: Smith, Jeffrey M.
• Position: Biodevastation - Essay

"With genetic engineering, transferring genes from one species' DNA to another is just like taking a page out of one book and putting it between the pages of another book." This popular analogy is used often by advocates of genetically modified (GM) food. The words on the page are made up of the four letters, or molecules, of the genetic code, which line up in "base pairs" along the DNA. The inserted page represents a gene, whose code produces one or more proteins. The book is made up of chapters, which represent chromosomes, large sections of DNA.

A groundbreaking report, however, shreds the book analogy. "Genome Scrambling--Myth or Reality?" written by three scientists at the UK--based Econexus, reveals that the process of genetic engineering results in widespread mutations-within the inserted gene, near its insertion, and in hundreds or thousands of locations throughout the genome--and that these are overlooked by many scientists and regulators. [1]

Gene insertion methods create mutations, fragments, and multiple copies

There are two popular methods for creating GM crops; both create mutations. The first method uses Agrobacterium, bacteria that contain circular pieces of DNA called plasmids. One section of this plasmid creates tumors. Under normal conditions, Agrobacterium infects a plant by inserting that tumor-creating portion into the plant's DNA. Genetic engineers, however, replace the tumor-creating section of the plasmid with one or more genes. They then use the altered Agrobacterium to infect a plant's DNA with those foreign genes.

The second method of gene insertion uses a gene gun. Scientists coat thousands of particles of tungsten or gold with gene sequences and then shoot these into thousands of plant cells. Years ago, the sequences that were shot into cells usually included both the genes that were intended for transfer (gene cassette) as well as extraneous DNA from the plasmid used in the creation and propagation of the cassettes in bacteria. This is true for most GM foods currently on the market. These days, many scientists take the added step of eliminating the extraneous, mostly bacterial DNA and coat the particles just with the cassette.

With both methods of gene insertion, scientists speculate that the process triggers a wound response in the plant cell, which helps its DNA integrate the foreign gene. With the gene gun technique, only a few cells out of thousands incorporate the foreign gene.

According to the book analogy, a single, intact, foreign page (gene) is inserted. That's the intention. In reality, most transformed DNA ends up with multiple copies of the foreign gene, incomplete genes and/or gene fragments. Sections of the inserted genes are commonly changed, rearranged, or deleted during the insertion process. In addition, extraneous pieces of plasmid DNA sometimes end up interspersed within and around the inserted gene or scattered throughout the genome.

Mutations near the site of insertion

The sections of the plant's DNA near the insertion site are almost always messed up in some way. This effect, called insertional mutagenesis, has been known for years, but it wasn't until 2003 that a large-scale systematic analysis was conducted. Researchers looked at insertions into 112 Arabidopsis thaliana plants, a species used often in plant research. [2] Although the study may not accurately reflect what...