Is Biologist Barry Commoner a Mutant?
January 30, 2002
By Ronald Bailey
Ronald Bailey is Reason's science correspondent and the editor of Earth Report 2000: Revisiting the True State of the Planet(McGraw-Hill)
Genes are not neat orderly sequences of DNA bases that are simply read off one by one. Instead, the DNA bases that make up a gene--called exons--are often interrupted by other DNA bases called introns that have nothing to do with the gene. In the first step in transcribing DNA into RNA, both exons and introns are read off to produce pre-messenger RNA. To get the proper recipe for a protein, the introns must be removed. That feat is accomplished by an editing machine composed of RNA and protein called the spliceosome that removes the introns and splices together the exons into mature messenger RNA that now embodies the proper recipe for a specific protein.
Alternative splicing occurs when regulatory elements in the genome perhaps tell the spliceosome to treat some introns as exons or some exons as introns, thus changing the protein recipe. As University of Georgia biologist Wayne Parrott notes, to a certain extent this is all a matter of nomenclature -- is it the "same" gene that is specifying different proteins or are they really different genes that happen to share overlapping DNA sequences? The fact is "there is still one DNA sequence per protein," says Parrott.
. . .there simply aren’t any "failures" in commercial plant biotechnology he can cite.
and Has Commoner any evidence that [problems] occurs frequently or at all in commercial biotech crops? If he does, he doesn’t cite it in Harper’s.
This is a bit of an exaggeration -- note the use of the word "frequently" and see the article.
To produce a commercial biotech crop variety, biotechnologists typically begin by producing hundreds and thousands of plants in which they are trying to insert a particular gene. Over the years they grow and select the ones in which the trait they are seeking -- say, pest resistance--is stable. Only after years of testing and research will they commercialize the selected crop variety.
. . . says biologist Parrott. "Transgenics cannot be different from conventional varieties." Biotech crops must be "substantially equivalent" to conventional varieties before they can be marketed. In every case, biotech companies have submitted reams of information to the Food and Drug Administration (FDA) on things like nutrient profiles and feeding values before marketing genetically enhanced crops.
"substantially equivalent"? Lots of wiggle room there.
Interestingly, scores of varieties of crops being grown today were produced through mutations induced by radiation and caustic chemicals in the 1940s and 1950s. No one knows what proteins these random genetic mutations produced, but people have been eating them for half a century without ill effects.
Yes, this is interesting.
Parrott points out that plant genomes are filled with DNA fragments called retrotransposons that naturally jump randomly from one part of a plant’s genome to another. These jumps occur billions of times every growing season. They often disrupt gene expression in plants and may well sometimes induce the production of novel proteins. But this is no cause for alarm, since people have been eating these crops with their jumping genomes for centuries. It is evident that such disruptions in plant genomes have an extremely low probability of producing any dangerous proteins.
Well, Jumping Genomes!!!
A year ago, it was fairly consistently reported that the human genome projects had counted some 30,000 - 40,000 human genes with, at that time, seemingly little dissent. This leads me to believe that there was a generally agreed-upon usage of the term "gene" and that what we may be seeing today is a redefinition of terms to more conform to expectations. But you all tell me . . .
The foregoing is not in any way the picture of simplicity and I would be most interested in hearing about the "guiding mechanism" that tells the splicosomes what to do and when. I think it's clear that there is much we do not understand, and that alone would appear to be sufficient reason for caution.