Ruthenium-Iinked DNA strands can make genetic testing cheap enough to be commonly employed
WITH threats of fatal diseases and genetic disorders on the rise, genetic testing becomes an essential tool in diagnosing an ailment or assessing the possibility of a person acquiring one. However, being prohibitively expensive, such speculative genetic screening is restrict- ed to patients in research projects or to those with a family history of the disease.
But researchers in USA have recently made some advances that brighten the prospects of screen- ing thousands of genes instantan- eously, thus allowing cheaper, rapid genetic tests for certain diseases on a large scale (Scientific American, Vol272, No 5).
Chemist Thomas J Meade and mol- ecular biologist Jon F Kayyem of the California Institute of Technology linked atoms of ruthenium, a heavy metal, to ribose, the sugar component of the DNA molecule without distorting its overall shape.
The ruthenium doped DNA double-helix acted like a piece of
live electrical wire. Contrary
to the estimation that DNA
molecule will conduct up
to hundred electrons a second, the current was up by
10,000 times, conducting over a million electrons a second.
Researchers discovered
that this new property of
DNA molecule to create a
highly conductive path
could help distinguish
among different DNA
sequences. Thus, the technique could hasten cheaper
and accurate testing of genes for certain diseases.
Using this technology, a
synth eticruthenium DNA strand could be used to
search for a particular gene sequence associated with a
specific disease.
If a matching complementary strand from the
disease-causing organism, for instance,
virus, were a
present, it would bind firmly to the
synthetic single DNA strand, built
specifically to duplicate any known
sequence. This would cause a high
flow of electrons to take place along
the molecule's axis and the molecule
will light up instantaneously like an
electrical indicator.
In case the genetic sequence under
search is absent, no current would flow
and so the detector would not glow.
Meade suspects that a device based
on such ruthenium-linked DNA would
require "between 15 and 20 bases of single-chain DNA deposited on a chip (of silicon)." Such a device, hopes Meade,
could allow simultaneous. detection of
hundreds of genes.
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