GMO Myths and Truths

When a fertilised ovum undergoes sister
chromatid exchange as part of conventional
breeding, the chromosome rearrangements do not
take place in a random and haphazard way, but
are precisely guided so that no information is lost.
There can be defects in the process, which could
lead to mutations. But the process works against
defects occurring by employing precise cellular
mechanisms that have evolved over hundreds
of thousands of years to preserve the order and
information content of the genome of the species.
Genetic engineering, on the other hand, is
an artificial laboratory procedure that forcibly
introduces foreign DNA into the cells of a plant.
Once the engineered transgene is in the nucleus of
the cells, it breaks randomly into the DNA of the
plant and inserts into that site. Furthermore, GM
plants do not contain only a few mutations. The
GM transformation process produces hundreds
or thousands of mutations throughout the plant’s
DNA.
For these reasons, conventional breeding is far
more precise and carries fewer mutation-related
risks than genetic engineering.
“We will select out harmful mutations”
GM proponents say that even if harmful
mutations occur, that is not a problem. They say
that during the genetic engineering process, the
GM plants undergo many levels of screening and
selection, and the genetic engineers will catch any
plants that have harmful mutations and eliminate
them during this process.
As explained above, the process of gene
insertion during the process of genetic
modification selects for engineered GM gene
insertion into active gene regions of the host
(recipient) plant cell. This means that the process
has a high inherent potential to disrupt the
function of active genes present in the plant’s
DNA.
In many cases, the disruption will be fatal
– the engineered cell will die and will not grow
into a GM plant. In other cases, the plant will
compensate for the lost function in some way, or
the insertion will occur at a location that seems
to cause minimal disruption of the plant cell’s
functioning. This is what is desired. But just
because a plant grows vigorously does not mean
that it is safe to eat and safe for the environment.
It could have a mutation that causes it to produce
substances that harm consumers or to damage the
ecosystem.
Genetic engineers do not carry out detailed
screening that would catch all potentially harmful
plants. They introduce the GM gene(s) into
hundreds or thousands of plant cells and grow
them out into individual GM plants. If the gene
insertion process has damaged the function of
one or more plant cell genes that are essential for
survival, the cell will not survive this process. So
plants carrying such “lethal” mutations will be
eliminated. But the genetic engineer is often left
with several thousand individual GM plants, each
of them different, because:
● The engineered genes have been inserted in
different locations within the DNA of each
plant
● Other mutations or disturbances in host gene
function have occurred at other locations in
the plants through the mechanisms described
above (1.3.4).
How do genetic engineers sort through the
GM plants to identify the one or two that they
are going to commercialise? The main thing
that they do is to verify that the trait that the
engineered transgene is supposed to confer has
been expressed in the plant. That is, they do a test
that allows them to find the few plants among the
many thousands that express the desired trait. Of
those, they pick one that looks healthy, strong,
and capable of being bred on and propagated.
That is all they do. Such screening cannot detect
plants that have undergone mutations that cause
them to produce substances that are harmful to
consumers or lacking in important nutrients.
It is unrealistic for GM proponents to claim
that they can detect all hazards based on
differences in the crop’s appearance, vigour, or
yield. Some mutations will give rise to changes
that the breeder will see in the greenhouse or field,
but others give rise to changes that are not visible
because they occur at a subtle biochemical level
or only under certain circumstances. So only a
small proportion of potentially harmful mutations
will be eliminated by the breeder’s superficial
GMO Myths and Truths 18