Biology once was regarded as a languid, largely descriptive
discipline, a passive science that was content, for much of its
history, merely to observe the natural world rather than change it.
No longer. Today biology, armed with the power of genetics, has
replaced physics as the activist Science of the Century and it stands
poised to assume godlike powers of creation, calling forth artificial
forms of life rather than undiscovered elements and sub-atomic
particles. The initial steps toward this new Genesis have been widely
touted in the press. It wasn't so long ago that Scottish scientists
stunned the world with Dolly, the fatherless sheep cloned directly
from her mother's cells: these techniques have now been applied,
unsuccessfully, to human cells. ANDi, a photogenic rhesus monkey,
recently was born carrying the gene of a luminescent jellyfish. Pigs
now carry a gene for bovine growth hormone and show significant
improvement in weight gain, feed efficiency, and reduced fat. Most
soybean plants grown in the United States have been genetically
engineered to survive the application of powerful herbicides. Corn
plants now contain a bacterial gene that produces an insecticidal
protein rendering them poisonous to earworms.
Our leading scientists and scientific entrepreneurs (two labels that
are increasingly interchangeable) assure us that these feats of
technological prowess, though marvelous and complex, are nonetheless
safe and reliable. We are told that everything is under control.
Conveniently ignored, forgotten, or in some instances simply
suppressed are the caveats, the fine print, the flaws and spontaneous
abortions. Most clones exhibit developmental failure before or soon
after birth, and even apparently normal clones often suffer from
kidney or brain malformations. ANDi, perversely, has failed to glow
like a jellyfish. Genetically modified pigs have a high incidence of
gastric ulcers, arthritis, cardiomegaly (enlarged heart), dermatitis,
and renal disease. Despite the biotechnology industry's assurances
that genetically engineered soybeans have been altered only by the
presence of the alien gene, as a matter of fact the plant's own
genetic system has been unwittingly altered as well, with potentially
dangerous consequences. The list of malfunctions gets little notice;
biotechnology companies are not in the habit of publicizing studies
that question the efficacy of their miraculous products or suggest the
presence of a serpent in the biotech garden.
The mistakes might be dismissed as the necessary errors that
characterize scientific progress. But behind them lurks a more
profound failure. The wonders of genetic science are all founded on
the discovery of the DNA double helix - by Francis Crick and James
Watson in 1953 - and they proceed from the premise that this molecular
structure is the exclusive agent of inheritance in all living things:
in the kingdom of molecular genetics, the DNA gene is absolute
monarch. Known to molecular biologists as the "central dogma" the
premise assumes that an organism's genome - its total complement of
DNA genes - should fully account for its characteristic assemblage of
inherited traits. The premise, unhappily, is false. Tested between
1990 and 2001 in one of the largest and most highly publicized
scientific undertakings of our time, the Human Genome Project, the
theory collapsed under the weight of fact. There are far too few
human genes to account for the complexity of our inherited traits or
for the vast inherited differences between plants, say, and people.
By any reasonable measure, the finding (published last February)
signaled the downfall of the central dogma; it also destroyed the
scientific foundation of genetic engineering, and the validity of the
biotechnology industry's widely advertised claim that its methods of
genetically modifying food crops are "specific, precise, and
predictable" and therefore safe. In short, the most dramatic
achievement to date of the $3 billion Human Genome Project is the
refutation of its own scientific rationale.
Since Crick first proposed it forty-four years ago, the central dogma
has come to dominate biomedical research. Simple, elegant and easily
summarized, it seeks to reduce inheritance, a property that only
living things possess, to molecular dimensions: the molecular agent of
inheritance is DNA, deoxyribonucleic acid, a very long, linear
molecule tightly coiled within each cell's nucleus. DNA is made up of
four different kinds of nucleotides, strung together in each gene in a
particular linear order of sequence. Segments of DNA comprise the
genes that, through a series of molecular processes, give rise to each
of our inherited traits.
Guided by Crick's theory, the Human Genome Project was intended to
identify and enumerate all of the genes in the human body by working
out the sequence of the three billion nucleotides in human DNA. In
1990, James Watson described the Human Genome Project as "the
ultimate description of life." It will yield, he claimed, the information
"that determines if you have life as a fly, a carrot, or a man."
Walter Gilbert, one of the project's earliest proponents, famously
observed that the 3 billion nucleotides found in human DNA would
easily fit on a compact disc, to which one could point and say, "here
is a human being; it's me!" President Bill Clinton described the
human genome as "the language in which God created life." How could
the minute dissection of human DNA into a sequence of 3 billion
nucleotides support such hyperbolic claims? Crick's crisply stated
theory attempts to answer that question. It hypothesizes a clear-cut
chain of molecular processes that leads from a single DNA gene to the
appearance of a particular inherited trait. The explanatory power of
the theory is based on an extravagant proposition: that the DNA genes
have unique, absolute, and universal control over the totality of
inheritance in all forms of life.
In order to control inheritance, Crick reasoned, genes would need to
govern the synthesis of protein, since proteins from the cell's
internal structures and, as enzymes, catalyze the chemical events that
produce specific inherited traits. The ability of DNA to govern the
synthesis of protein is facilitated by their similar structures - both
are linear molecules composed of specific sequences of subunits. A
particular gene is distinguished from another by the precise linear
order (sequence) in which the four different nucleotides appear in its
DNA. In the same way, a particular protein is distinguished from
another by the specific sequence of the twenty different kinds of
amino acids of which it is made. The four kinds of nucleotides can be
arranged in numerous possible sequences, and the choice of any one of
them in the makeup of a particular gene represents its "genetic
information" in the same sense that, in poker, the order of a hand of
cards informs the player whether to bet high on a straight or drop out
with a meaningless set of random numbers.
Crick's "sequence hypothesis" neatly links the gene to the protein:
the sequence of the nucleotides in a gene "is a simple code for the
amino acid sequence of a particular protein." This is shorthand for a
series of well-documented molecular processes that transcribe the gene's DNA nucleotide sequence into a complementary sequence of
ribonucleic acid (RNA) nucleotides that, in turn, delivers the gene's
code to the site of protein formation, where it determines the
sequential order in which the different amino acids are linked to form
the protein. It follows that in each living thing there should be a
one-to-one correspondence between the total number of genes and the
total number of proteins. The entire array of human genes - that is,
the genome - must therefore represent the whole of a person's
inheritance, which distinguishes a person from a fly, or Walter
Gilbert from anyone else. Finally, because DNA is made of the same
four nucleotides in every living thing, the genetic code is universal,
which means that a gene should be capable of producing its particular
protein wherever it happens to find itself, even in a different
species.
Crick's theory includes a second doctrine, which he originally called
the "central dogma" (though this term is now generally used to
identify his theory as a whole). The hypothesis is typical Crick:
simple precise, and magisterial. "Once (sequential) information has
passed into protein it cannot get out again." This means that genetic
information originates in the DNA nucleotide sequence and terminates,
unchanged, in the protein amino acid sequence. The pronouncement is
crucial to the explanatory power of the theory because it endows the
gene with undiluted control over the identity of the protein and the
inherited trait that the protein creates. To stress the importance of
their genetic taboo, Crick bet the future of the entire enterprise on
it, asserting that "the discovery of just one type of present-day
cell" in which genetic information passed from protein to nucleic
acid or from protein to protein "would shake the whole intellectual
basis of molecular biology."
Crick was aware of the brashness of his bet, for it was known that in
living cells proteins come into promiscuous molecular contact with
numerous other proteins and with molecules of DNA and RNA. His
insistence that these interactions are genetically chaste was designed
to protect the DNA's genetic message - the gene's nucleotide
sequence - from molecular intruders that might change the sequence or
add new ones as it was transferred, step by step, from gene to protein
and thus destroy the theory's elegant simplicity.
Last February, Crick's gamble suffered a spectacular loss. In the
journals Nature and Science, and at joint press conferences and
television appearances, the two genome research teams reported their
results. The major result was "unexpected." Instead of the 100,000
or more genes predicted by the estimated number of human proteins, the
gene count was only about 30,000. By this measure, people are only
about as gene-rich as a mustardlike weed (which has 26,000 genes) and
about twice as genetically endowed as a fruit fly or a primitive
worm - hardly an adequate basis for distinguishing among "life as a
fly, a carrot, or a man." In fact, an inattentive reader of genomic
CDs might easily mistake Walter Gilbert for a mouse, 99 percent of
whose genes have human counterparts.
The surprising results contradicted the scientific premise on which
the genome project was undertaken and dethroned its guiding theory,
the central dogma. After all, if the human gene count is too low to
match the number of proteins and the numerous inherited traits that
they engender, and if it cannot explain the vast inherited difference
between a weed and a person, there must be much more to the "ultimate
description of life" than the genes, on their own, can tell us.
Scientists and journalists somehow failed to notice what had happened.
The discovery that the human genome is not much different from the
roundworm's, led Dr. Eric Lander, one of the leaders of the project,
to declare that humanity should learn "a lesson in humility." In the
New York Times, Nicholas Wade merely observed that the project's
surprising results will have an "impact on human pride" and that
"human self-esteem may be in for further blows" from future genome
analyses, which had already found that the genes of mice and men are
very similar.
The project's scientific reports offered little to explain the
shortfall in the gene count. One of the possible explanations for why
the gene count is "so discordant with our predictions" was described,
in full, last February in Science as follows: "nearly 40% of human
genes are alternatively spliced." Properly understood, this modest,
if esoteric, account fulfills Crick's dire prophecy: it "shakes the
whole intellectual basis of molecular biology" and undermines the
scientific validity of its applications to genetic engineering.
Alternative splicing is a startling departure from the orderly design
of the central dogma, in which the distinctive nucleotide sequence of
a single gene encodes the amino acid sequence of a single protein.
According to Crick's sequence hypothesis, the gene's nucleotide
sequence (i.e., its "genetic information") is transmitted, altered in
form but not in content, through RNA intermediaries, to the
distinctive amino acid sequence of a particular protein. In
alternative splicing, however, the gene's original nucleotide sequence
is split into fragments that are then recombined in different ways to
encode a multiplicity of proteins, each of them different in their
amino acid sequence from each other and from the sequence that the
original gene, if left intact, would encode.
The molecular events that accomplish this genetic reshuffling are
focused on a particular stage in the overall DNA-RNA-protein,
progression. It occurs when the DNA gene's nucleotide sequence is
transferred to the next genetic carrier - messenger RNA. A
specialized group of fifty to sixty proteins, together with five small
molecules of RNA - known as a "spliceosome" - assembles at sites
along the length of the messenger RNA, where it cuts apart various
segments of the messenger RNA. Certain of these fragments are spliced
together into a number of alternative combinations, which then have
nucleotide sequences that differ from the gene's original one. These
numerous, redesigned messenger RNAs govern the production of an equal
number of proteins that differ in their amino acid sequence and hence
in the inherited traits that they engender. For example, when the
word TIME is rearranged to read MITE, EMIT, and ITEM, three
alternative units of information are created from an original one.
Although the original word (the unspliced messenger RNA nucleotide
sequence) is essential to the process, so is the agent that performs
the rearrangement (the spliceosome).
Alternative splicing can have an extraordinary impact on the
gene/protein ratio. We now know that a single gene originally
believed to encode a single protein that occurs in cells of the inner
ear of chicks (and of humans) gives rise to 576 variant proteins,
differing in their amino acid sequences. The current record for the
number of different proteins produced from a single gene by
alternative splicing is held by the fruit fly, in which one gene
generates up to 38,016 variant protein molecules.
Alternative splicing thus has a devastating impact on Crick's theory:
it breaks open the hypothesized isolation of the molecular system that
transfers genetic information from a single gene to a single protein.
By rearranging the single gene's nucleotide sequence into a
multiplicity of new messenger RNA sequences, each of them different
from the unspliced original, alternative splicing can be said to
generate new genetic information. Certain of the spliceosome's
proteins and RNA components have an affinity for particular sites and,
binding to them, form an active catalyst that cuts the messenger RNA
and then rejoins the resulting fragments. The spliceosome proteins
thus contribute to the added genetic information that alternative
splicing creates. But this conclusion conflicts with Crick's second
hypothesis - that proteins cannot transmit genetic information to
nucleic acid (in this case, messenger RNA) - and shatters the elegant
logic of Crick's interlocking duo of genetic hypotheses.
The discovery of alternative splicing also bluntly contradicts the
precept that motivated the genome project. It nullifies the
exclusiveness of the gene's hold on the molecular process of
inheritance and disproves the notion that by counting genes one can
specify the array of proteins that define the scope of human
inheritance. The gene's effect on inheritance thus cannot be
predicted simply from its nucleotide sequence - determination of which
is one of the main purposes of the Human Genome Project. Perhaps this
is why the crucial role of alternative splicing seems to have been
ignored in the planning of the project and has been obscured by the
cunning manner in which its chief result has been reported. Although
the genome reports do not mention it, alternative splicing was
discovered well before the genome project was even planned - in 1978
in virus replication, and in 1981 in human cells. By 1989, when the
Human Genome Project was still being debated among molecular
biologists, its champions were surely aware that more than 200
scientific papers on alternative splicing of human genes had already
been published. Thus, the shortfall in the human gene count could -
indeed should - have been predicted. It is difficult to avoid the
conclusion - troublesome as it is - that the project's planners knew in
advance that the mismatch between the numbers of genes and proteins in
the human genome was to be expected, and that the $3 billion project
could not be justified by the extravagant claims that the genome - or
perhaps God speaking through it - would tell us who we are.
Alternative splicing is not the only discovery over the last forty
years that has contradicted basic precepts of the central dogma.
Other research has tended to erode the centrality of the DNA double
helix itself, the theory's ubiquitous icon. In their original
description of the discovery of DNA, Watson and Crick commented that
the helix's structure "immediately suggests a possible copying
mechanism for the genetic material." Such self-duplication is the
crucial feature of life, and in ascribing it to DNA, Watson and Crick
concluded, a bit prematurely, that they had discovered life's magic
molecular key.
Biological replication does include the precise duplication of DNA,
but this is accomplished by the living cell, not by the DNA molecule
alone. In the development of a person from a single fertilized egg,
the egg cell and the multitude of succeeding cells divide in two.
Each such division is precede by a doubling of the cell's DNA; two new
DNA strands are produced by attaching the necessary nucleotides
(freely available in the cell), in the proper order, to each of the
two DNA strands entwined in the double helix. As the single
fertilized egg cell grows into an adult, the genome is replicated many
billions of times, its precise sequence of three billion nucleotides
retained with extraordinary fidelity. The rate of error - that is,
the insertion into the newly made DNA sequence of a nucleotide out of
its proper order - is about one in 10 billion nucleotides. But on its
own, DNA is incapable of such faithful replication; in a test-tube
experiment, a DNA strand, provided with a mixture of its four
constituent nucleotides, will line them up with about one in a hundred
of them out its proper place. On the other hand, when the appropriate
protein enzymes are added to the test tube, the fidelity with which
nucleotides are incorporated in the newly made DNA strand is greatly
improved, reducing the error rate to one in 10 million. These
remaining errors are finally reduced to one in 10 billion by a set of
"repair" enzymes (also proteins) that detect and remove mismatched
nucleotides from the newly synthesized DNA.
Thus, in the living cell the gene's nucleotide code can by replicated
faithfully only because an array of specialized proteins intervenes to
prevent most of the errors - which DNA by itself is prone to make -
and to repair the few remaining ones. Moreover, it has been known
since the 1960s that the enzymes that synthesize DNA influence its
nucleotide sequence. In this sense, genetic information arises not
from DNA alone but through its essential collaboration with protein
enzymes - a contradiction of the central dogma's precept that
inheritance is uniquely governed by the self-replication of the DNA
double helix.
Another important divergent observation is the following: in order to
become biochemically active and actually generate the inherited trait,
the newly made protein, a strung-out ribbon of a molecule, must be
folded up into a precisely organized ball-like structure. The
biochemical events that give rise to genetic traits - for example,
enzyme action that synthesizes a particular eye-color pigment - take place
at specific locations on the outer surface of the three-dimensional
protein, which is created by the particular way in which the molecule
is folded into that structure. To preserve the simplicity of the
central dogma, Crick was required to assume, without any supporting
evidence, that the nascent protein - a linear molecule - always folded
itself up in the right way once its amino acid sequence had been
determined. In the 1980s, however, it was discovered that some
nascent proteins are on their own likely to become misfolded - and
therefore remain biochemically inactive - unless they come in contract
with a special type of "chaperone" protein that properly folds them.
The importance of these chaperones has been underlined in recent years
by research on degenerative brain diseases that are caused by
"prions," research that has produced some of the most disturbing
evidence that the central dogma is dangerously misconceived. Crick's
theory holds that biological replication, which is essential to an
organism's ability to infect another organism, cannot occur without
nucleic acid. Yet when scrapie, the earliest known such disease, was
analyzed biochemically, no nucleic acid - neither DNA nor RNA - could
by found in the infectious material that transmitted the disease. In
the 1980's, Stanley Prusiner confirmed that the infectious agents that
cause scrapie, mad cow disease, and similar very rare but invariably
fatal human diseases are indeed nucleic-acid-free proteins (he named
them prions), which replicate in an entirely unprecedented way.
Invading the brain, the prion encounters a normal brain protein which
it then refolds to match the prion's distinctive three-dimensional
shape. The newly refolded protein itself becomes infectious and,
acting on another molecule of the normal protein, sets up a chain
reaction that propagates the disease to its fatal end.
The prion's unusual behavior raises important questions about the
connection between a protein's amino acid sequence and its
biochemically active, folded-up structure. Crick assumed that the
proteins' active structure is automatically determined by its amino
acid sequence (which is, after all, the sign of its genetic
specificity), so that two proteins with the same sequence ought to be
identical in their activity. The prion violates this rule. In a
scrapie-infected sheep, the prion and the brain protein that it
refolds have the same amino acid sequence, but one is a normal
cellular component and the other is a fatal infectious agent. This
suggests that the protein's folded-up configuration is, to some
degree, independent of its amino acid sequence and therefore
determined, in part, by something other than the DNA gene that
governed the synthesis of that sequence. And since the prion protein'
s three-dimensional shape is endowed with transmissible genetic
information, it violates another fundamental Crick precept as well -
the forbidden passage of genetic information from one protein to
another. Thus, what is known about the prion is a somber warning
that processes far removed from the conceptual constraints of the
central dogma are at work in molecular genetics and can lead to fatal
disease.
By the mid 1980s, therefore, long before the $3 billion Human Genome
Project was funded, and long before genetically modified crops began
to appear in our fields, a series of protein-based processes had
already intruded on the DNA gene's exclusive genetic franchise. An
array of protein enzymes must repair the all-too-frequent mistakes in
gene replication and in the transmission of the genetic code to
proteins as well. Certain proteins, assembled in spliceosomes, can
reshuffle the RNA transcripts, creating hundreds and even thousands of
different proteins from a single gene. A family of chaperones,
proteins that facilitate the roper folding - and therefore the
biochemical activity - of newly made proteins, form an essential part
of the gene-to-protein process. By any reasonable measure, these
results contradict the central dogma's cardinal maxim: that a DNA
gene exclusively governs the molecular processes that give rise to a
particular inherited trait. The DNA gene clearly exerts an important
influence on inheritance, but it is not unique in that respect and
acts only in collaboration with a multitude of protein-based processes
that prevent and repair incorrect sequences, transform the nascent
protein into its folded, active form, and provide crucial added
genetic information well beyond that originating in the gene itself.
The net outcome is that no single DNA gene is the sole source of a
given protein's genetic information and therefore of the inherited trait.
The credibility of the Human Genome Project is not the only casualty
of the scientific community's stubborn resistance to experimental
results that contradict the central dogma. Nor is it the most
significant casualty. The fact that one gene can give rise to
multiple proteins also destroys the theoretical foundation of a
multibillion-dollar industry, the genetic engineering of food crops.
In genetic engineering it is assumed, without adequate experimental
proof, that a bacterial gene for an insecticidal protein, for example,
transferred to a corn plant, will produce precisely that protein and
nothing else. Yet in that alien genetic environment, alternative
splicing of the bacterial gene might give rise to multiple variants of
the intended protein - or even to proteins bearing little structural
relationship to the original one, with unpredictable effects on
ecosystems and human health.
The delay in dethroning the all-powerful gene led in the 1990s to a
massive invasion of genetic engineering into American agriculture,
though its scientific justification had already been compromised a
decade or more earlier. Nevertheless, ignoring the profound fact that
in nature the normal exchange of genetic material occurs exclusively
within a single species, biotech-industry executives have repeatedly
boasted that, in comparison, moving a gene from one species to another
is not only normal but also more specific, precise, and predictable.
In only the last five years such transgenic crops have taken over 68
percent of the US soybean acreage, 26 percent of the corn acreage, and
more than 69 percent of the cotton acreage.
That the industry is guided by the central dogma was made explicit by
Ralph W.F. Hardy, president of the National Agricultural Biotechnology
Council and formerly director of life sciences at DuPont, a major
producer of genetically engineered seeds. In 1999, in Senate
testimony, he succinctly described the industry's guiding theory this
way: "DNA (top management molecules) directs RNA formation (middle
management molecules) directs protein formation (worker molecules)."
The outcome of transferring a bacterial gene into a corn plant is
expected to be as predictable as the result of a corporate takeover: what the workers do will be determined precisely by what the new top
management tells them to do. This Reaganesque version of the central
dogma is the scientific foundation upon which each year billions of
transgenic plants of soybeans, corn, and cotton are grown with the
expectation that the particular alien gene in each of them will be
faithfully replicated in each of the billions of cell divisions that
occur as each plant develops; that in each of the resultant cells the
alien gene will encode only a protein with precisely the amino acid
sequence that it encodes in its original organism; and that throughout
this biological saga, despite the alien presence, the plant's natural
complement of DNA will itself be properly replicated with no abnormal
changes in composition.
In an ordinary unmodified plant the reliability of this natural
genetic process results from the compatibility between its gene system
and its equally necessary protein-mediated systems. The harmonious
relation between the two systems develops during their cohabitation,
in the same species, over very long evolutionary periods, in which
natural selection eliminates incompatible variants. In other words,
within a single species the reliability of the successful outcome of
the complex molecular process that gives rise to the inheritance of
particular traits is guaranteed by many thousands of years of testing,
in nature.
In a genetically engineered transgenic plant, however, the alien
transplanted bacterial gene must properly interact with the plants'
protein-mediated systems. Higher plants, such as corn, soybeans, and
cotton, are known to possess proteins that repair DNA miscoding;
proteins that alternatively splice messenger RNA and thereby produce a
multiplicity of different proteins from a single gene; and proteins
that chaperone the proper folding of other, nascent proteins. But the
plant systems' evolutionary history is very different from the
bacterial gene's. As a result, in the transgenic plant the harmonious
interdependence of the alien gene and the new host's protein-mediated
systems is likely to be disrupted in unspecified imprecise and
inherently unpredictable ways. In practice, these disruptions are
revealed by the numerous experimental failures that occur before a
transgenic organism is actually produced and by unexpected genetic
changes that occur even when the gene has been successfully
transferred.
Most alarming is the recent evidence that in a widely grown
genetically modified food crop - soybeans containing an alien gene for
herbicide resistance - the transgenic host plant's genome has itself
been unwittingly altered. The Monsanto Company admitted in 2000 that
its soybeans contained some extra fragments of the transferred gene,
but nevertheless concluded that "no new proteins were expected or
observed to be produced." A year later, Belgian researchers
discovered that a segment of the plant's own DNA had been scrambled.
The abnormal DNA was large enough to produce a new protein, a
potentially harmful protein.
One way that such mystery DNA might arise is suggested by a recent
study showing that in some plants carrying a bacterial gene, the plant
's enzymes that correct DNA replication errors rearrange the alien
gene's nucleotide sequence. The consequences of such changes cannot
be foreseen. The likelihood in genetically engineered crops of even
exceedingly rare, disruptive effects of gene transfer is greatly
amplified by the billions of individual transgenic plants already
being grown annually in the United States.
The degree to which such disruptions do occur in genetically modified
crops is not known at present, because the biotechnology industry is
not required to provide even the most basic information about the
actual composition of the transgenic plants to the regulatory
agencies. No tests, for example, are required to show that the plant
actually produces a protein with the same amino acid sequence as the
original bacterial protein. Yet, this information is the only way to
confirm that the transferred gene does in fact yield the
theory-predicted product. Moreover, there are no required studies
based on detailed analysis of the molecular structure and biochemical
activity of the alien gene and its protein product in the transgenic
commercial crop. Given that some unexpected effects may develop very
slowly, crop plants should be monitored in successive generations as
well. None of these essential tests are being performed, and billions
of transgenic plants are now being grown with only the most
rudimentary knowledge about the resulting changes in their
composition. Without detailed, ongoing analyses of the transgenic
crops, there is no way of knowing if hazardous consequences might
arise. Given the failure of the central dogma, there is no assurance
that they will not. The genetically engineered crops now being grown
represent a massive uncontrolled experiment whose outcome is
inherently unpredictable. The results could be catastrophic.
Crick's central dogma has played a powerful role in creating both the
Human Genome Project and the unregulated spread of genetically
engineered food crops. Yet as evidence that contradicts this
governing theory has accumulated, it has had no effect on the
decisions that brought both of these monumental undertakings into
being. It is true that most of the experimental results generated by
the theory confirmed the concept that genetic information, in the form
of DNA nucleotide sequences, is transmitted from DNA via RNA to
protein. But other observations have contradicted the one-to-one
correspondence of gene to protein and have broken the DNA gene's
exclusive franchise on the molecular explanation of heredity. In the
ordinary course of science, such new facts would be woven into the
theory, adding to its complexity, redefining its meaning, or, as
necessary, challenging its basic premise. Scientific theories are
meant to be falsifiable; this is precisely what makes them scientific
theories. The central dogma has been immune to this process.
Divergent evidence is duly reported and, often enough generates
intense research, but its clash with the governing theory is almost
never noted.
Because of their commitment to an obsolete theory, most molecular
biologists operate under the assumption that DNA is the secret of
life, whereas the careful observation of the hierarchy of living
processes strongly suggests that it is the other way around: DNA did
not create life; life created DNA. When life was first formed on the
earth, proteins must have appeared before DNA because, unlike DNA,
proteins have the catalytic ability to generate the chemical energy
needed to assemble small ambient molecules into larger ones such as
DNA. DNA is a mechanism created by the cell. Early life survived
because it grew, building up its characteristic array of complex
molecules. It must have been a sloppy kind of growth; what was newly
made did not exactly replicate what was already there. But once
produced by the primitive cell, DNA could become a stable place to
store structural information about the cell's chaotic chemistry,
something like the minutes taken by a secretary at a noisy committee
meeting. There can be no doubt that the emergence of DNA was a
crucial stage in the development of life, but we must avoid the
mistake of reducing life to a master molecule in order to satisfy our
emotional need for unambiguous simplicity. The experimental data,
shorn of dogmatic theories, points to the irreducibility of the living
cell, the inherent complexity of which suggests that any artificially
altered genetic system, given the magnitude of our ignorance, must
sooner or later give rise to unintended, potentially disastrous,
consequences. We must be willing to recognize how little we truly
understand about the secrets of the cell, the fundamental unit of
life.
Why, then, has the central dogma continued to stand? To some degree
the theory has been protected from criticism by a device more common
to religion than science; dissent, or merely the discovery of a
discordant fact, is a punishable offense, a heresy that might easily
lead to professional ostracism. Much of this bias can be attributed
to institutional inertia, a failure of rigor, but there are other,
more insidious, reasons why molecular geneticists might be satisfied
with the status quo; the central dogma has given them such a
satisfying, seductively simplistic explanation of heredity that it
seemed sacrilegious to entertain doubts. The central dogma was simply
too good not to be true.
As a result, funding for molecular genetics has rapidly increased over
the last twenty years, new academic institutions, many of them
"genomic" variants of more mundane professions, such as public health,
have proliferated. At Harvard and other universities, the biology
curriculum has become centered on the genome. But beyond the
traditional scientific economy of prestige and the generous funding
that follows it as night follows day, money has distorted the
scientific process as a once purely academic pursuit has been
commercialized to an astonishing degree by the researchers themselves.
Biology has become a glittering target for venture capital; each new
discovery brings new patents, new partnerships, and new corporate
affiliations. But as the growing opposition to transgenic crops
clearly shows, there is persistent public concern not only with the
safety of genetically engineered foods but also with the inherent
dangers in arbitrarily overriding patterns of inheritance that are
embedded in the natural world through long evolutionary experience.
Too often those concerns have been derided by industry scientists as
the "irrational" fears of an uneducated public. The irony, of course,
is that the biotechnology industry is based on science that is forty
years old and conveniently devoid of more recent results, which show
that there are strong reasons to fear the potential consequences of
transferring a DNA gene between species. What the public fears is not
the experimental science but the fundamentally irrational decision to
let it out of the laboratory into the real world before we truly
understand it.
Barry Commoner is senior scientist at the Center for Biology of
Natural Systems at Queen's College, City University of New York where
he directs the Critical Genetics Project.
Readers can obtain a list of references used as sources for this article by sendin a request to: cbns@cbns.qc.edu
Copyright 2002 Harpers Magazine
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