GMO Myths and Truths

mutagenesis. This can occur in a number of different ways:
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The GM gene can be inserted into the middle of one of the plant’s natural genes. Typically
this blocks the expression of – “knocks out” – the natural gene, destroying its function.
Less frequently the insertion event will alter the natural plant gene’s structure and the
structure and function of the protein for which it encodes.
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The GM gene can be inserted into a region of the plant’s DNA that controls the expression
of one or more genes of the host plant, unnaturally reducing or increasing the level of
expression of those genes.
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Even if the GM gene is not directly inserted into a gene of the host plant or its control
elements, its mere presence within a region of the plant’s DNA where host genes are
located and active can alter the normal pattern of gene function – that is, the level at
which a given gene is switched on. Thus it can alter the balance of the genes’ resulting
protein products. The inserted gene can compete with gene expression control elements
within the DNA of the host plant for the binding of regulatory proteins. The result will
be marked disturbances in the level and pattern of expression of the host plant’s natural
genes.
Since the insertion of the GM gene is an imprecise and uncontrolled process, there is no way
of predicting or controlling which of the plant’s genes will be influenced and how.
2. Genome-wide mutations
In most cases, the insertion process is not clean. In addition to the intended insertion,
fragments of DNA from the GM gene cassette can be inserted at multiple random locations
in the genome of the host plant. Each of these unintended insertions is a mutational event
that can disrupt or destroy the function of other genes in the same ways as the full GM gene,
described under “Insertional mutagenesis”, above.
It is estimated that there is a 53–66% probability that any insertional event will disrupt a
gene. 1 Therefore, if the genetic modification process results in one primary insertion and
two or three unintended insertions, it is likely that at least two of the plant’s genes will be
disrupted.
Evidence from research indicates that the genetic modification process can also trigger other
kinds of mutations – rearrangements and deletions of the plant’s DNA, especially at the site
of insertion of the GM gene cassette 1 – which are likely to compromise the functioning of
genes important to the plant.
3. Mutations caused by tissue culture
Three steps of the genetic modification process take place while the host plant cells are being
grown in a process called cell culture or tissue culture. These steps include:
1. The initial insertion of the GM gene cassette into the host plant cells
2. The selection of plant cells into which the GM gene cassette has been successfully
inserted
GMO Myths and Truths 36