GENETIC ENGINEERING

Genetic engineering (GE) is used to take genes and segments of DNA from one
species, e.g. fish, and put them into another species, e.g. tomato. To do
so, GE provides a set of techniques to cut DNA either randomly or at a
number of specific sites. Once isolated one can study the different segments
of DNA, multiply them up and splice them (stick them) next to any other DNA
of another cell or organism. GE makes it possible to break through the
species barrier and to shuffle information between completely unrelated
species; for example, to splice the anti-freeze gene from flounder into
tomatoes or strawberries, an insect-killing toxin gene from bacteria into
maize, cotton or rape seed, or genes from humans into pig.

Yet there is a problem - a fish gene will not work in tomato unless I give
it a promoter with a "flag" the tomato cells will recognise. Such a control
sequence should either be a tomato sequence or something similar. Most
companies and scientists do a shortcut here and don't even bother to look
for an appropriate tomato promoter as it would take years to understand how
the cell's internal communication and regulation works. In order to avoid
long testing and adjusting, most genetic engineering of plants is done with
viral promoters. Viruses - as you will be aware - are very active. Nothing,
or almost nothing, will stop them once they have found a new victim or
rather host. They integrate their genetic information into the DNA of a host
cell (such as one of your own), multiply, infect the next cells and
multiply. This is possible because viruses have evolved very powerful
promoters which command the host cell to constantly read the viral genes and
produce viral proteins. Simply by taking a control element (promoter) from a
plant virus and sticking it in front of the information block of the fish
gene, you can get this combined virus/fish gene (known as a "construct') to
work wherever and whenever you want in a plant.

This might sound great, the drawback though is that it can't be stopped
either, it can't be switched off. The plant no longer has a say in the
expression of the new gene, even when the constant involuntary production of
the "new" product is weakening the plant's defences or growth.

And furthermore, the theory doesn't hold up with reality. Often, for no
apparent reason, the new gene only works for a limited amount of time and
then "falls silent". But there is no way to know in advance if this will
happen.

Though often hailed as a precise method, the final stage of placing the new
gene into a receiving higher organism is rather crude, seriously lacking
both precision and predictability. The "new" gene can end up anywhere, next
to any
gene or even within another gene, disturbing its function or regulation. If
the "new" gene gets into the "quiet" non-expressed areas of the cell's DNA,
it is likely to interfere with the regulation of gene expression of the
whole region. It could potentially cause genes in the "quiet" DNA to become
active.

Often genetic engineering will not only use the information of one gene and
put it behind the promoter of another gene, but will also take bits and
pieces from other genes and other species. Although this is aimed to benefit
the expression and function of the "new" gene it also causes more
interference and enhances the risks of unpredictable effects.

How to get the gene into the other cell.

There are different ways to get a gene from A to B or to transform a plant
with a "new" gene. A VECTOR is something that can carry the gene into the
host, or rather into the nucleus of a host cell. Vectors are commonly
bacterial plasmids (see below and next page) or viruses (a). Another method
is the "SHOTGUN TECHNIQUE" also known as "bio-ballistics," which blindly
shoots masses of tiny gold particles coated with the gene into a plate of
plant cells, hoping to land a hit somewhere in the cell's DNA (b).

What is a plasmid?

PLASMIDS can be found in many bacteria and are small rings of DNA with a
limited number of genes. Plasmids are not essential for the survival of
bacteria but can make life a lot easier for them. Whilst all bacteria - no
matter which species - will have their bacterial chromosome with all the
crucial hereditary information of how to survive and multiply, they invented
a tool to exchange information rapidly. If one likens the chromosome to a
bookshelf with manuals and handbooks, and a single gene to a recipe or a
specific building instruction, a plasmid,could be seen as a pamphlet.
Plasmids self-replicate and are thus easily reproduced and passed around.
Plasmids often contain genes for antibiotic resistance. This type of
information which can easily be passed on, can be crucial to bacterial
strains which are under attack by drugs and is indeed a major reason for the
quick spread of antibiotic resistance.

Working with plasmids.

Plasmids are relatively small, replicate very quickly and are thus easy to
study and to manipulate. It is easy to determine the sequence of its DNA,
that is, to find out the sequence of the letters (A, C, G and 1) and number
them. Certain letter combinations -such as CAATTG - are easy to cut with the
help of specific enzymes (see proteins). Ilese cutting enzymes, called
restriction enzymes, are part of the Genetic Engineering "tool-kit" of
biochemists. So if I want to splice a gene from fish into a plasmid, I have
to take the following steps: I place a large number of a known plasmid in a
little test tube and add a specific enzyme that will cut the plasmid at only
one site. After an hour I stop the digest, purify the cut plasmid DNA and
mix it with copies of the fish gene; after some time the fish gene places
itself into the cut ring of the plasmid. I quickly add some "glue" from my
"tool-kit" - an enzyme called ligase - and place the mended plasmids back
into bacteria, leaving them to grow and multiply. But how do I know which
bacteria will have my precious plasmid? For this reason I need MARKER GENES,
such as antibiotic resistance genes. So I make sure my plasmid has a marker
gene before I splice my fish gene into it. If thA I plasmid is marked with a
gene antibiotic resistance I can now add specific antibiotic to the food
supply of the bacteria. All those which do not have the plasmid will die,
and all those that do have the plasmid will multiply.

Unanswered Questions and Inherent Uncertainties

What's wrong with Genetic Engineering ?

Genetic Engineering is a test tube science and is prematurely applied in
food production. A gene studied in a test tube can only tell what this gene
does and how it behaves in that particular test tube. It cannot tell us what
its role and behaviour are in the organism it came from or what it might do
if we place it into a completely different species. Genes for the colour red
placed into petunia flowers not only changed the colour of the petals but
also decreased fertility and altered the growth of
the roots and leaves. Salmon genetically engineered with a growth hormone
gene not only grew too big too fast but also turned green. These are
unpredictable side effects, scientifically termed pleiotropic effects.

We also know very little about what a gene (or for that matter any of its
DNA sequence) might trigger or interrupt depending on where it got inserted
into the new host (plant or animal). These are open questions around
positional effects. And what about gene silencing and gene instability? How
do we know that a genetically engineered food plant will not produce new
toxins and allergenic substances or increase the level of dormant toxins and
allergens? How about the nutritional value? And what are the effects on the
environment and on wild life? All these questions are important questions
yet they remain unanswered. Until we have an answer to all of these, genetic
engineering should be kept to the test tubes. Biotechnology married to
corporations tends to ignore the precautionary principle but it also igpores
some basic scientific principles.

What you can do:

þ Avoid genetically engineered (GE) food, currently in products containing
soya and maize.

þ Buy organic products - look for the Soil Association label.

þ Tell your MP and the Minister of the Environment you object to GE crops
being released on test sites in your area -or any area you care about. Ask
your MP or the Department of Environment, Transport and the Regions (DETR)
for details from the Public Register of GMOs (genetically modified
organisms). DETR phone: 0171-890 5275.

þ Copy this briefing and give it to a neighbour /friend.

þ Contact your local paper; write a letter to the editor.

þ Demand clear choice and non-GE products from your supermarket