From: Gina Miller (echoz@hotmail.com)
Date: Fri Apr 23 1999 - 14:07:52 MDT
Dna-based Chips Diagnose Disease-- And Raise Hackles
The Sacramento Bee
It looks like a run-of-the-mill silicon computer chip. It's flat,
dark gray and no bigger than a thumbnail. But this is a very special
chip: Its job is to find out whether people are likely to get cancer.
Similar chips are being made for other diseases, including AIDS,
leukemia and tuberculosis, and eventually there will be chips that
will even predict the behavioral traits of unborn babies.
DNA chip technology is a burgeoning new area of medicine and genetics
that promises to revolutionize disease diagnosis. But it is also
generating growing controversy, with calls for international controls
to make sure it is not abused.
Current laboratory techniques for detecting genetic mutations that
are responsible for disease are time-consuming and expensive, taking
months, even years. In contrast, a DNA chip takes minutes, or at most
hours, to seek out disease-causing mutations in genes.
Though the technology is complex, the theory behind the process is
simple. Instead of having intricate microelectronic circuits etched
onto their surfaces, these tiny chips are coated with DNA sequences,
some of which are associated with a healthy gene while others are
known disease-causing mutations.
The sequences, up to 400,000 on a single tiny chip, line up in the
squares of a grid on the surface of the chip. A sample of the
patient's DNA is then put onto the chip and each sequence pairs off
with its opposite number. Whether or not they are exactly the same as
their partner is then detected by a laser.
A patient whose DNA exactly matches with a known mutation on the chip
may be at risk from that particular disease. If the DNA fails to
match with a known healthy sequence, that can also indicate potential
problems.
"It is incredibly rapid. What you are relying on is that you will
recognize differences between the DNA on the chip and DNA you are
looking at. In terms of a quick screen, it is masterful because it
gives you a quick answer and it is cheap," says Dr. Gareth Evans,
consultant geneticist at Christie's Hospital in Manchester, England.
Half a dozen companies are now working on producing variations of
these chips and California-based Affymetrix has launched three for
use by researchers. The jewel in the crown at present is a chip that
works on a gene called p53 that is abnormal in more than half of all
types of cancers.
At the Houston Advanced Researcher Center, Dr. Dat Dao and a team of
researchers are working on chips that will be able to pinpoint
antibiotic-resistant strains of TB. Another chip detecting mutations
linked to breast cancer is in the pipeline, and the center is also
working on one that will take some of the uncertainty out of matching
donor tissue for bone marrow transplants.
"This genosensor technology is going to create a host of benefits for
the diagnosis of cancer as well as genetic and infectious diseases.
It is going to be the diagnostic tool of the future," says Dao.
Dr. Mike Ramsay of the Oak Ridge National laboratory in Tennessee,
who also works with DNA chips, agrees: "This technology could be used
to screen for people carrying genes that predispose them to getting
breast cancer, becoming obese, or having children with cystic
fibrosis. To make such an analysis we eventually hope to require only
a few white blood cells or skin cells."
But the rapidly evolving technology is seen by some as a Pandora's
box, with almost as many ethical dilemmas as benefits. One of the
biggest fears is that the chips will be seen as the ideal tool for
the establishment of widespread genetic screening of all types and
for all kinds of motives.
"Today's supply of screening for young couples is restricted to
cystic fibrosis and a few rare diseases that are confined to specific
populations. The chip, however, will broaden the spectrum of
analyzable parental traits practically ad libitum," says Dr. Wolfram
Henn, a clinical geneticist at the University of Hamburg in Germany
who raised concerns about the technology in this month's Journal of
Medical Ethics.
The chief area for concern is prenatal screening, where DNA chips,
the developers claim, will make it possible to test for every disease
and trait in an unborn baby.
"The subjective choice of genetic traits that are considered as
prenatal selection criteria may blur the distinction between
preventative medicine and striving for the perfectly designed child,"
he says.
(Copyright 1999)
_____via IntellX_____
Publication Date: April 22, 1999
Powered by NewsReal's IndustryWatch
Gina "Nanogirl" Miller
Nanotechnology Industries
Web Page
http://www.nanoindustries.com
E-mail
echoz@hotmail.com
Alternate E-mail
nanogirl@halcyon.com
"The science of nanotechnology, solutions for the future."
_______________________________________________________________
Get Free Email and Do More On The Web. Visit http://www.msn.com
This archive was generated by hypermail 2.1.5 : Fri Nov 01 2002 - 15:03:37 MST