Scrambling and Gambling with the Genome
by Jeffrey M. Smith (Author of
Seeds of Deception)
August 2005
“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.
The analogy makes the process of genetic engineering appear to
be as simple and precise as inserting a new page. 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]
The report is an extensive review of research that overturns
the central arguments by biotech advocates—that the technology
is precise, predictable, and safe, and that current studies
are adequate. On the contrary, it demonstrates that GM crops
represent a significant gamble to public health and the
environment (see www.econexus.info).
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 is designed to create 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 end 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
In addition to the changes made in the material that is
inserted, the sections of the plant’s DNA near the insertion
site are almost always messed up in some way. This effect,
called insertional mutagenesis or insertion mutation, 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 happens in edible crop plants,
it is the only large study at this point.
Plants were selected that had single copies of the foreign
gene, which were inserted using Agrobacterium. Of the
112 plants, 80 (71%) had small mutations near the insertion
site. These included deletions of 1-100 base pairs and/or
insertions of 1-100 extraneous base pairs. The inserted
sequences came from the foreign gene, extraneous parts of the
plasmid, or other parts of the plant’s DNA.
The remaining 32 plants (29%) had large scale insertions,
rearrangements, duplications and/or deletions. In two plants,
parts of whole chromosomes had broken off and translocated
into another section of the DNA.
Another study using the same plant species also found that a
section of DNA at least 40,000 base pairs long had
translocated from one chromosome to another. In fact, that
long section had duplicated itself, since it was also found
intact in its original position. [3] A third study identified
a deletion of 75,800 base pairs, which probably contained 13
genes. [4]
The above studies used the Agrobacterium insertion
method. There have been astoundingly few studies analyzing
insertion mutations resulting from the gene gun method, but
the research that has been conducted consistently demonstrate
large scale disruptions of the DNA. According to the Econexus
report, “The vast majority of the insertion events created via
particle bombardment [gene gun] are extremely complex, with
multiple copies of transgenic DNA inserted at a single
insertion-site.”1
They contain large amounts of extraneous DNA, including
multiple fragments of the foreign gene and/or small or large
fragments of plant DNA interspersed with the inserted genes.
In one study, scientists found 155 separate breaks indicating
recombinations of the inserted genetic material. [5]According
to the Econexus report, in the rare cases where only a single
copy of the foreign gene is inserted, they “turn out to
contain fragments of superfluous DNA and/or they appear to be
associated with large deletions and/or rearrangements of the
target plant DNA.” 1
One study on gene gun insertion revealed that DNA of an oat
plant contained the full sequence of the foreign gene plasmid,
a small stretch in which oat DNA was mixed up with foreign
plasmid DNA, a partial copy of the plasmid, and another
section with oat and plasmid sequences scrambled together. [6]
Analysis also indicated that the plant’s DNA on either side of
the insertion contained rearrangements or deletions. There
were also two other insertions elsewhere in the DNA. One
included a rearranged section of the plasmid (296 base pairs),
scrambled plant DNA on either side, and the deletion of 845
base pairs. The study employed DNA sequence analysis, the most
thorough method for evaluating insertion mutations. In
practice, it is rarely used. Instead, genetic engineers
traditionally rely on the less precise Southern blot test,
which picks up only major changes in DNA sequence. When this
test had been applied to the oat DNA above, it indicated the
presence of only a single intact inserted gene. It failed to
identify the other two insertions and all of the mutations and
fragments. This means that on the whole, biologists who create
GM plants have no idea of the extent to which their creations
may produce unintended side effects do to scrambled DNA.
Location, Location, Location
Neither gene insertion method can “aim” the foreign gene into
a particular location in the DNA. Furthermore, scientists
rarely conduct experiments to find out where exactly the
inserted genes end up. But in the real estate of the DNA,
location is vital. The functioning of the foreign gene can
change dramatically, depending on where in the genome it is
located. The side-effects of gene insertion can be
significantly influenced by location as well.
Even though only an estimated 1-10% of plant DNA constitutes
the genes, Agrobacterium insertions end up inside
functioning gene sequences between 35%-58% of the time. (The
percentage for gene guns is unknown.) Genes are also inserted
in other areas that influence gene expression. In either case,
insertions can significantly disrupt the normal functioning of
the plant’s genes.
(One reason why insertions end up inside genes so often is
that in order for the foreign genes to function, they need to
be located within the regions of the host DNA that are
“active,” that allow gene expression. To figure out which
inserted genes end up in these portions of the DNA, scientists
typically add an antibiotic resistant marker (ARM) gene to the
genetic cassette. After insertion, they apply antibiotics to
all the cells, killing those that don’t have a functioning ARM
gene in their DNA. Since the active region of the DNA is also
where the plant’s functioning genes are located, those that
survive this selection process are more likely to have foreign
genes lodged inside the host genes.)
Mutations Throughout the DNA
Once genes are inserted into a plant cell’s DNA, scientists
typically grow the cell into a fully functioning plant using a
method called tissue culture. Unfortunately, this artificial
method of plant propagation results in widespread mutations
throughout the genome. In fact, tissue culture is sometimes
used specifically to create mutations in plant DNA. These
mutations can influence the crops’ height, resistance to
disease, oil content, number of seeds, and many other traits.
[7][8]
Genetically modified cells that undergo tissue culture can
have even more mutations throughout the genome than cultured
non-GM cells. It is unclear why gene insertion has this
effect, but scientists speculate that it may, in part, come
from unsuccessful insertions or insertions of small fragments.
Taken together, the process of gene insertion combined with
tissue culture typically results in hundreds or thousands of
mutations, including small deletions, substitutions, or
insertions in the genetic code. The changes are vast. Two
studies suggested that 2-4% of the genome of a GM plant was
different than non-GM controls. [9][10] Furthermore, estimates
are based on detection methods that miss many mutations such
as short deletions and insertions and most base pair
substitutions. Thus, the actual degree of gene disruption is
probably greater.
These genome-wide mutations are found in every GM plant
analyzed. Astoundingly, these types of mutations are not
evaluated in commercially released GM food crops.
If the original GM plant is crossed (mated) with other lines
over and over, many of these small, genome-wide mutations will
get corrected. It is unknown, however, how many mutations
still persist in food crops. Furthermore, the propagation of
certain species, such as the GM potato that was on the market
years ago, probably did not undergo any outcrossing, and it is
likely to contain all of the mutations created during
insertion and tissue culture.
Mutations Can Have Serious
Consequences
Mutations and extraneous insertions carry risk. They can
permanently turn genes on or off, alter their function, and/or
change the structure or function of the protein that they
create. A single mutation can influence many genes
simultaneously. Thus, the insertion process might cause the
over production of toxins, allergens, carcinogens, or
anti-nutrients, reduce the nutritional quality of the crop, or
change the way that the plant interacts with its environment.
And because of our limited understanding of the DNA, even if
we knew which parts of it were disrupted, we wouldn’t
necessarily know the consequences.
In addition, the insertion of bacterial plasmid DNA into plant
DNA creates another serious risk. Similarities in the genetic
sequence between the plasmid and the DNA of bacteria found in
the gut of humans or animals or in the soil might
significantly increase the likelihood of horizontal gene
transfer. This means that genes from the plant may transfer
into the DNA of the soil or gut bacteria. The only human
feeding study on genetic engineering confirmed that the genes
inserted into GM soybeans do transfer into the bacteria inside
human intestines.
Advocates of biotechnology often defend the safety of their
products by claming that modern methods of plant breeding
other than genetic engineering are used on a wide scale,
have a history of safe use and create comparable mutations.
The Econexus report reveals that everything about this
argument is pure speculation and is not supported by
scientific literature. There is no evidence that these
modern methods are used widely, are consistently safe, or
create mutations of the same kind or frequency as genetic
engineering.
In reality, many biotech scientists are unaware of the massive
quantity of mutations that are generated by the GM
transformation process (gene insertion and tissue culture). In
fact, the regulatory agencies that approve GM foods operate as
if the insertion process has no impact on safety. [11][12]
They do not require extensive evaluation of the mutations and
therefore the extent of these in approved GM food crops has
not been identified. The few studies that have been conducted
revealed many significant problems. GM varieties contain
truncated or multiple fragments of the inserted gene and
extraneous or scrambled DNA. One GM corn variety contained a
fragment from a gene that was supposed to be inserted into a
different GM variety. The protein produced by the foreign
genes can also be truncated, altered, or fragmented. And many
significant differences between GM and non-GM crops have been
observed, which may result from the insertion process. An
approved GM squash, for example, contains 68 times less
beta-carotene and four times more sodium than non-GM squash.
GM soybeans have much higher levels of a potential allergen
and anti-nutrient. But GM crops are tested for only a handful
of nutrients or known toxins, and therefore the true impact of
gene mutations is not known. Furthermore, GM plants are grown
in vast amounts. Undetected alterations may result in harm to
the environment or human health on an unprecedented scale.
With so little known about the impact of gene insertion, and
with so much at risk, applying genetic engineering to food and
crops is a huge gamble.
Revised Book Analogy
With genome scrambling in mind, let’s revise the book analogy
as follows:
The DNA is like a large book with the letters consisting of
the four molecules that make up the genetic code. Located
throughout the book are special one- to two-page passages,
called genes, which describe characters called proteins
(including enzymes). The book is divided into chapters called
chromosomes.
When a single foreign page (gene) is inserted through the
process called genetic engineering, the book goes through a
profound transformation. There are typos throughout, in
hundreds or thousands of places. Letters are switched here and
there; words and sentences are scrambled, deleted, repeated or
reversed. Long and short passages from one part of the book
may be relocated or repeated elsewhere, and bits of text from
entirely different books show up from time to time. As you get
close to the inserted page, things get really strange. The
story becomes indecipherable. The text includes random letters
and sections of inserted foreign text, and several pages are
missing. The inserted page may actually be multiple identical
pages, partial pages, or small bits of text, sections that are
misspelled, deleted, inverted, and scrambled. As a result of
changes in the story line throughout the book, several
characters (proteins) act differently, sometimes switching
roles from heroes to villains, or vice versa. It all makes you
wonder about the comment made by the biotech advocate as he
handed you the volume, “It’s just the same old book, only with
a single page added.”
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