Re: Re: CULT - Genetic Engineering

The worries expressed about the genetic engineering of corn are unlikely to
effect irises in the ways Walter (with tongue in cheek so far he might bite
it off) worried about.

The engineered corn has had a gene inserted from the bacterium Bacillus
thuringensis ("Bt"), which we have long used as a pesticide.  Bt produces a
protien toxin that attacks the guts of a range of insect pests.  Different
strains of the bacterium can be used to kill cabbage worms, corn borers,
corn earworms, and even Japanese beetles (but this is not the same as milky
spore disease).

The nutritional value of the corn is unchanged and so far as we know, Bt
toxin is not directly harmful to either animals or humans.

However, there are two possible concerns.  The Bt toxin is structurally
similar to the protien which is responsible for some serious food allergies
(such as those to peanuts, which can be rapidly fatal in sensitive
individuals), though there are no known cases of reactions by humans to Bt
toxin.  It is likely that the toxin is destroyed by cooking or at least
altered to the point that it would not provoke a reaction.  The toxin does
not pass through animals that are fed the engineered corn, but is broken
down in their digestive systems.  Nevertheless, thorough testing would be
needed before the corn could be ajudged safe for human consumption.

The second concern is that by exposing large pest populations to the Bt
toxin, we could hasten the development of resistance to it, and thus lose a
valuable adjunct in the battle against insect pests.

Advantages, of course, are many.  The greatest from an environmental
standpoint is that farmers can use much less of the more dangerous
pesticides and still produce lots of good clean corn.

Some people are concerned about lateral gene transfer, the movement of
genes from one species to another, possibly carried by viruses that can
infect multiple hosts.  This might not be such a problem with Bt in corn,
but engineered cotton with herbicide resistance could allow the
herbicide-resistance gene to enter populations of weeds.  We don't know of
any viruses that infect both humans (or any vertebrate) and plants.

The Law of Unintended Consequences is still not much heeded by industrial
researchers, despite some disasterous failures.  On the other side we have
irresponsible panic-mongers who decry any attempt to improve food yields by
"unnatural" methods, whatever that means.  The two groups tend to balance
off somewhat and eventually we get a usable solution.....


Bill Shear
Department of Biology
Hampden-Sydney College
Hampden-Sydney VA 23943
(804)223-6172
FAX (804)223-6374
email<wshear@email.hsc.edu>
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