DNA fibs

April 2014

Photo from Creative Commons

The original, and biggest, fib about GM plants is perpetrated to this day.  It is the wildly inaccurate image of genetic engineers simply 'snipping' a natural gene out of one organism and popping it into another, to create a crop with a precise genetic 'improvement'.

Such genetic improvements popped into the GM plants which have been commercialised to date have been 'snipped' almost exclusively from bacterial genomes.

In the ideal biotech world, DNA is just DNA and is common to all classes of organism.  All classes of organism use the self-same gene-to-protein synthetic mechanism.  Therefore, a bacterial gene snipped out and popped into a plant will generate a bacterial protein just as it did in its native bug.  The details go something like this ...

Genes are made of DNA. DNA consists of a chain of 'nucleic acid' chemical units (these are the 'NA' part of DNA).  The sequence of nucleic acids in a gene forms a template which is used to send instructions out into the cell to create a protein.  Proteins consist of a chain of 'amino-acid' chemical units.  If a genetic engineer knows the amino-acid sequence in the desired protein, he can work out the appropriate DNA template which will send out the appropriate instructions to the cell to generate the protein.  Simple.

Or, is life ever that straightforward?

DNA in bacteria may appear chemically very similar to DNA in plants, but if you snip out a bacterial gene and pop it into a plant, you'll find very little happens.  This is because bacterial DNA only produces bacterial proteins which work in bacteria, and plants only produce plant proteins which work in plants.

The distinction seems to lie in subtle differences in the DNA sequences in different organisms.

Different strands of DNA with numerous small changes in their sequence can, in fact, create proteins with exactly the same sequence of amino-acids.  Such chemically-identical proteins generated from dissimilar DNAs have, however, proven to exhibit very different properties: for example, two chemically-identical proteins may exhibit different enzymic activity, or may induce different allergic reactions.

Such variations arise because the DNA not only dictates the protein's amino-acid sequence but contains information on how the protein is manufactured.  Differences in the manufacturing process will, for instance, alter how the protein folds into its active 3-dimensional shape leading to profound changes in its final function.

Bacterial proteins don't work in plants because they're shaped like bacterial proteins and will only fit into bacterial metabolic pathways.

To convert bacterial proteins into plant proteins, genetic engineers have to build themselves DNA templates with extensive chemical adaptations (no, there's no 'snipping' involved).  They may even find it necessary to change some of the amino-acids in the GM protein before a plant-active form is achieved.  Artificial DNA constructs also routinely need powerful viral DNA 'promoters' added on to force the novel gene to generate a protein.  At the end of the day, the alterations are so extensive, that “the gene for the original source protein is hardly recognizable” (Cummins).

Any notion of a GM crop containing a simple, 'natural' gene 'snipped' from another organism is patent nonsense. 

And any notion that the GM plant protein must be safe just because the natural bacterial gene and its protein are, is the biggest fib around.

Scarily, a GM plant protein is only ever safety-tested using a protein with something approximating the same amino-acid sequence produced by bacteria.

The possibility that a plant's GM protein has unique toxic or allergenic regions absent from the natural bacterial version is very real.

OUR COMMENT

Another concern has long been the question of stability of artificial DNA once it's out in the field and subject to environmental stresses and evolutionary pressures.

GM enzymes may well not be stabilised by the plants' intrinsic repair mechanisms, and may have altered activity (even if the amino-acid sequence is unchanged).  In such cases, an accumulation of toxic by-products or the promotion of disease are to be expected.

As we've said before, this year's safe GM food could be next year's disease and famine.

If you don't want to face the consequences of 'next year's' GM offering, make this clear to everyone responsible for your food supply.

For some other fun things you never wanted to know about the 'precisely' engineered DNA  inside a GM plant, check out DNA WOBBLIES - (Online document link) GMFS Archive, March 2008.

SOURCE:

Prof. Joe Cummins, New Hazards in GMOs from Synonymous Mutations, Institute of Science in Society Report, 25.11.13