DNA Joe Job
10th May 2004
A regular Joe Job is when a spam run is forged to appear as
though it came from an innocent party's domain, which is
then generally flooded by the bounces. A DNA Joe Job is
similar in some respects but with potentially far more
serious consequences for the victim and society as a whole.
An educational biotechnology kit designed to teach students
about recombinant DNA technology via hands-on experiments
appeared on the market a few years ago.
Recombinant DNA technology allows a piece of foreign DNA to
be inserted into a bacterium. By that means, for example, it
is possible to harvest human insulin from bacteria growing
in a fermentor.
The kit enables students to insert a piece of their own DNA
into the ubiquitous gut bacterium Escherichia coli. It does
so by using a small circle of DNA called a plasmid as the
vector (i.e. delivery system).
Plasmids are found in most types of bacteria along with a
single much larger loop of somatic DNA that determines the
bacterium's species. A plasmid carries one or more genes
that confer a survival advantage to the host, such as, for
example, resistance to an antibiotic.
A bacterium can contain thousands of plasmids, each of
which can be passed to members of its own and other
species. Useful plasmids propagate quickly through
bacterial colonies.
Bacteria also contain restriction endonuclease enzymes that
cut DNA at specific sites and ligase enzymes that join such
cut pieces together.
The kit exploits all of this bacterial biochemistry and
includes a plasmid carrying two genes that confer resistance
to the antibiotics ampicillin and kanamycin, respectively.
The resistance genes, when used with the antibiotics, enable
the students to identify and isolate the bacteria that have
taken up the modified plasmids prepared during various
experiments.
The kit's capabilities bore a striking similarity to
classified work carried out at places like Porton Down where
biological weapons are developed using virtually the same
techniques.
The kit allows high school students to easily carryout
genetic experiments that took hundreds of leading scientists
using expensive and sophisticated equipment many years to
research and develop. A kit costs a few dollars and fits
comfortably into a pocket.
It soon became apparent that the kit also provided the means
to carry out the ultimate Joe Job using DNA rather than a
domain name.
Criminal DNA profiling (or fingerprinting) works by
measuring the lengths of Short Tandem Repeats (STRs) found
within human DNA using a process known as PCR. The lengths
of approximately 500 STR variations, known as alleles, at
ten (UK) or thirteen (US) locations makes up a DNA profile.
Those STR allele molecules are between 50 and 500 base pairs
in length.
With access to the necessary equipment, it is possible to
synthesise the allele molecules used in profiling (custom-
designed allele molecules can also be purchased online). The
molecules require special "sticky ends" so that the DNA
ligase enzyme can join them together. Eventually, a long
strand of DNA carrying profiling alleles and their PCR
primer binding sites can be created.
Custom designed DNA molecules with the correct sticky ends
can be substituted for the student's own DNA at the point in
the experiment where human DNA is inserted into the
plasmids. The experiment results in a culture of E. coli
containing a section of DNA carrying human criminal
profiling alleles. The spiked plasmids can be taken up by
many other species of bacteria, too.
Billions of the modified bacteria can then be bred in a home
made fermentor. Every bacterium that acquires the modified
plasmid also acquires an antibiotic resistance gene and the
survival advantage it confers. Modified E coli will swap
plasmids with other species of bacteria. In the environment,
STR-loaded plasmids will eventually pass to bacteria that
spread via airborne spores and be blown across the planet.
Strains of bacteria carrying specially encoded DNA sequences
have already been released into the environment by Porton
Down scientists, who have also developed customised PCR
primers to identify the tagged biological agents used in
dispersal experiments.
The opportunities for mischief are endless. The full
profile of a particular individual could be inserted into a
plasmid thereby giving the impression that he or she was
present at every crime scene contaminated with their
personalised bacteria.
Random collections of human alleles can be inserted into
common bacteria found in homes, on human skin and within
body cavities (causing bad breath, urinary infections, etc)
or in the gut of birds, rodents, flies and household pets.
They would eventually become widespread posing serious
problems for agencies relying on DNA profiling to identify
criminals.
Apart from human allele sequences, plasmids could contain
tens of thousands of modified PCR primer sequences. Their
PCR amplification products would bind to the forward and
reverse primers and to the template DNA primer sites thereby
blocking the amplification of one or more targeted alleles.
The fact that such bacteria exist (or might exist) could
introduce difficulties for prosecutors and new defence
arguments for those defendants against whom DNA evidence is
adduced. It might also cause jurors to pause before
accepting the myth of infallibility that has come to be
associated with forensic DNA evidence.
The next time someone discards a cigarette butt or a used
tissue, he or she could become the most famous Joe Job
victim on the planet.
Author's details -
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miracle cure, silent killer or weapon of mass destruction?
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