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A paper published in June 2007 by a consortium of
scientists from 80 research organisations has provided evidence that genes do
not necessarily behave in a linear fashion with information flowing one way,
from DNA to RNA to protein, as was thought till now. This central dogma that has
been the bedrock of genetics and the foundation on which the genetic engineering
industry is based, has been challenged by a growing collection of data but
scientists have been reluctant to revise the scientific principles established
by the Watson-Crick discovery of the structure of DNA and the subsequent
understanding of gene function.
Now, unequivocal evidence comes from research organised by
the US National Human Genome Research Institute, which has found that the human
genome is not really a clear and organised set of genes but rather a tangle of
overlapping, interacting genetic material that functions as a complex network,
with highly nuanced gene regulation. Almost none of these mechanisms are
understood. Not being able to predict how genes will behave strikes at the very
basis of using genetic engineering as a tool to create new products. The
biotechnology industry is built on the linear model of the “one gene, one
protein” principle, postulated by scientists who created recombinant DNA in the
1970s. Earlier, it was thought that genes had clearly defined functions,
therefore a gene from any organism could fit neatly and predictably into any
other organism, however unrelated, and carry on its prescribed business. In this
way, the Bt gene that produces a toxin in a soil bacterium is presumed to
perform exactly the same function when inserted into cotton, or rice plants.
The new research shows that this assumption cannot be
upheld. The use of genetic engineering to create new products rests on the
presumption that there is a universal, genetic code that sets the rules for
creating proteins from DNA and that the rules are virtually identical across all
organisms. Even before this research on the human genome, the theory of a
uniform system for making new proteins was challenged by a number of
scientific discoveries like the presence of large amounts
of ‘junk DNA’ in all organisms and the fact that the highly complex human
organism was found to have just 30,000 genes, a fairly small number considering
the myriad functions a human being performs.
The new research casts the spotlight on the role of ‘junk
DNA’, the large amounts of DNA detected during genome sequencing for which no
clear functions can be ascribed. It is now accepted that the so-called “junk”
DNA has a key regulatory role and it is of critical importance in regulating
gene expression in organisms, a process about which there is as yet little
understanding.
Apart from the new evidence and the presence of junk DNA,
there are other findings that challenge the one gene-one protein foundation of
agricultural biotechnology. One of these is the discovery that DNA is not the
sole hereditary material and not the only means of transmitting information for
new protein synthesis.
Understanding of the Mad Cow Disease and its link with the
human Jakob-Creutzfeldt disease shows that both diseases can be passed from
generation to generation not via genes, but via a protein molecule called a ‘prion’.
Pioneering work done in the
US by Stanley Prusiner, Susan
Lindquist and Eric Kandel indicates that prions mediate a form of protein-based
information flow, which seems to be important in a variety of biological
processes. To all this, if we add what is being discovered about the other ways
in which RNA acts and the process of RNA interference, the reliability of
genetic engineering becomes questionable. RNA’s normal role is to carry a
message from the DNA to the cytoplasm where it provides the direction for making
proteins. Now it appears that ordinary RNA can enter a cell, seek out a gene’s
protein making template and then destroy it. This process is called RNA
interference.
A complex, interactive network of genetic material
incorporating so-called ‘junk DNA’, prions as units of heredity and the
phenomenon of RNA interference, invalidates the premise on which agricultural
(and other) biotechnology has been founded. Evidence that gene expression is
complex and non-linear begins to explain why so many things go wrong during the
process of genetic engineering and why predicting its outcome remains a gamble.
This opens up the question about the extent to which genetic engineering can be
considered accurate and predictable as a ‘manufacturing process’. What else is
transmitted along with genes and how do these factors determine the outcome? How
do genes actually function in the new environment and can one ever hope to
control the complex regulatory mechanisms that come into play once a gene, or
many genes, are engineered into another background?
Suman Sahai |
