GENTECH archive


Re: Risks GE-food vs. Conventional breeding

Anything in quotes followed by <Wytze> was written by Wytze de Lange

Wytze de Lange wrote:

"Dear mr. Deelstra,
I took a look at the website you mention below. I went to the section:
genetic engineering versus conventional breeding. It contains no news
for me, except the arguments got even worse. Before, the argument was
that genetic engineering was better than cellfusion, where varieties
from the same species are fused that do not mix naturally anymore. I
agreed with the fact that cellfusion is a very doubtfull technique.
However, since all the risks are not known it is not possible to say
what is worse. To argue now that GE is better than conventional
breeding, because it is more precise is really saying: "we are better
than nature" or for religious people "we are better than God"."

Analogy: To state that cycling is a more efficient way of transport
than is walking in terms of energy required/covered distance isn't
really saying that 'We (?) are better than Nature and/or God'. The
technology is just better suited for our needs  than natural
locomotion. With needs as applied to crop breeding I mean; accuracy,
speed and ease of 'implementation' of a particular trait.

"Well, if you share that position, I have a few questions to you:
please explain me in all details all about what happens in
conventional breeding.  I want to see your 100% understanding. I also
would like to see the 100% understanding of what happens in GE."

100% is a lot, but I'll try. (BTW: Do you have a 100% understanding of
conventional breeding and cellular processes in plants? Many GE
activists assume (a priori) that conventional breeding is safe. But
why do they? Is it the deeply rooted myth that anything natural just
because of being natural is healthier and/or better than anything made
by man?)

I will use pest and disease resistance as an example in the following.
The problem in developing such resistant strains is that many features
that render a plant resistant to pests and disease often render the
plant less eatable (due to extensive lignification, production of
phytoalexins, terpenes, alkaloids etc). I quote: "[...], the very
defense compounds that increase the evolutionary fitness of plants by
warding off fungi, bacteria, and herbivores also make them undesirable
as food for humans. Agriculturally important crop plants have been
artificially selected for producing relatively low levels of these
compounds. This, of course, makes them all the more susceptible to
insects and disease." (#1)
Transferring resistance from a wildtype (wt) plant to a cultivated
variety by conventional breeding may result in a surprisingly toxic
plant, especially if the basis of resistance was not known. Even if
the basis of resistance is known and known to be safe conventional
breeding can introduce transposable elements from the wildtype strain
and unknown genes in close proximity of the 'resistance' gene will be
very very hard to breed out (a phenomenon called linkage
With GE the resistance gene will be isolated, sequenced etc and if
necessary modified to suit the host. These transferred genes and their
products are often well characterised. The only genes/ DNA-sequences
transferred with the gene of interest are regulatory sequences and
selection markers (used to select transfected plants*; I think leaving
bacterial selection markers to select e.g. A. tumefaciens is a bad
habit). After transfection/transformation the introduced gene will
recombine into a random site in the genome of a plant
(illegitimate/heterologous recombination). This integration can (1)
inactivate genes by inserting into them and (2) influence the
expression of other genes by inserting into regulatory sequences or
(3) do nothing if the DNA inserts into the large(!) part of the DNA
that confers no (known) function. However illegitimate recombination
can also occur in conventional breeding techniques (not to mention the
'danger' of transposons). In GE, the site(s) of integration can be
determined by several techniques and determining the sequence around
the site can show possible insertions into genes or regulatory
elements. It is than a matter of testing clones to find one with
satisfying expression and minimal or no side effects.

"The webpage states something like: the genetic structure of man,
animals, plants and bacteria are identical. Do you know what is meant
by that? To my knowledge this statement is either wrong or at least
not the full truth and certainly not the only point to take into
consideration and therefore wrong. I learn that genes are NOT the
same, they have differences." <Wytze>

I think the page ment that (1) the chemical constitution of DNA is
essentially the same (A,T,G,C) and (2) all units in the genome are
something like promoter-code for polypeptide-terminator. The last
simplified scheme is extensively modified in eukaryotes but one can
(more or less) easily modify bacterial genes to accommodate for those
changes. More problematic are posttranslational events like cleavage,
glycosylation, folding and disulphide bonding. This is however a
larger problem when expressing eukaryotic proteins in prokaryotes than
vice versa. Researchers of course  test for those kind of things
because these problems could render a protein inactive.

"My point is: Mankind has lived since its beginning on conventional
breeding." <Wytze>

IMHO: I don't think you have a point. What we did since the beginning
of mankind should not be a guidance in our planning of today or the
future. Some traits are very hard to get into plants. To disable
pectinase in tomatoes one can wait for a mutant (can take a very long
time) or use UV or chemical mutagenesis (=conventional breeding). The
last method will result not only in the inactivation of the pectinase
gene but also in countless unknown mutations in the whole genome of
the plant. With GE one can insert an anti-sense RNA and voila;
sufficiently lowered levels of pectinase. Control (e.g. tissue/time
specific expression) of the construct will also be more precise than
in a UV or wildtype mutant.

"Official policy is that GE foods should be not less safe than
conventional food, that's something else than  "the benefits outweigh
the risks" as the website does. Whose benefits?? Whose risks?? Do you
know?" <Wytze>

Saying that food or anything else is safe is an oversimplification of
the world around us. Nothing is absolutely safe; nor GE, nor
conventional breeding nor breathing or whatsoever.

If safe is such a major issue  I myself would plee for a case by case
testing of new crops (GE or conventional)
(BTW have you ever read a thorough test of broccoli? Yet it was
quickly accepted by consumers!)

(#1) L. Taiz & E Zeiger. Plant Physiology. p321 'Secondary Plant
Products'. The Benjamin/Cummings Publishing Company, Inc.

* an alternative selection marker would be a gene that conferred
resistance to herbicides (e.g. glyfosfate resistant EPSP synthase)