By JUSTIN POPE, AP Business Writer - (Published September 7, 2003)
WOBURN, Mass. (AP) - It's been three years since scientists
completed a rough draft of the human genetic code,
but nobody's rushing out yet for a personal DNA analysis. That's because the first draft took 12 years and cost
billions of dollars.
Today, the cost has fallen, but only
to around $50 million. The target price is orders of magnitude away:
an individual's DNA sequence.
That's the price considered essential
for giving scientists the thousands of sequenced samples they need to
understand how genes work, and giving patients access to a personalized DNA snapshot at the doctor's office
that could show the diseases they are at risk of developing.
Some scientists believe the old methods of sequencing DNA,
though improving, will never produce a $1,000
genome, and they are exploring radically different ways to map the blueprint of human life.
Their methods remain far from proven. But there have lately been signs of headway on several fronts.
"It's not clear which of these things will be the ultimate
success, but I think these are all pieces of the puzzle
moving us in the direction we need to go," said Jeff Schloss, program director for technology development at the
National Institutes of Health's National Human Genome Research Institute.
The human genome project yielded
the first complete sequence of the 3.2 billion base pairs that comprise
molecule of a person (actually, it sequenced a composite of a few people). Each base is one of four chemicals,
their order governing a human being's development.
But that was only a starting point.
While the DNA of one person is 99.9
percent identical to another's, it is the 0.1 percent of variation that
many scientists because the differences may answer questions like why some people develop certain diseases
and others do not.
To answer those questions, scientists must compare the
DNA sequences of thousands of people. To get them,
they must find a way to sequence DNA that, unlike the first sequencing, doesn't require thousands of lab
technicians and dozens of supercomputers.
"To actually deliver everybody's genome, you can't apply
that kind of brute force strategy," said George Church, a
researcher at Harvard Medical School.
For years, scientists sequencing DNA have relied on a lumbering
technique called electrophoresis. But it requires
expensive chemicals, and without expensive hardware an average lab would be hard-pressed to sequence more
than 1,000 base pairs a day. At that speed, it would take almost 10,000 years to get through the 3.2 billion base
pairs in human DNA.
The new techniques start from scratch.
In April, a group led by Caltech researcher Stephen Quake
published the first successful results from "single
molecule sequencing," or reading DNA one base pair at a time. Quake's group uses a fluorescent label to mark the
free molecules that surround DNA, then tracks which molecules are used when the DNA makes a copy of itself. The
technique works on only five base pairs at a time, but Quake says many sequences can be read at once.
Meanwhile, in an article published in the August edition
of Science, Church's lab reported progress on bathing DNA
in different frequencies of light to produce a color-coded snapshot revealing the order of a DNA sequence.
Daniel Branton, a Harvard colleague of Church, is working
on a method Schloss considers among the most
promising: shooting DNA through a tiny hole called a nanopore and measuring the electric signals each base pair
And in another recent development, a Branford, Conn., company
called 454 Life Sciences announced it had
sequenced the genome of a virus - about 30,000 base pairs long - by dropping DNA into tiny wells, and is now
working on bacteria, with 2 million to 8 million base pairs. The company hopes to work its way up to humans.
Other technologies can compare one strand to a reference,
like that provided by the human genome project, and
highlight differences. That could help scientists identify the 99.9 percent of identical base pairs, and allow them to
focus on the remaining 0.1 percent.
Woburn-based U.S. Genomics, for example, tags certain sequences
then shoots them past a laser, which detects
the tags as they go by.
Many of these techniques solve some shortcomings of electrophoresis,
but none solves them all. Knotty obstacles
remain, like "blurring" of the base pairs' fluorescence, or finding computers that can crunch all the numbers these
One skeptic, Elaine Mardis, a genetics expert at Washington
University in St. Louis, worries that too many labs are
releasing "data by press release" rather than subjecting the information to scientific review. She isn't convinced
that scientists are solving problems such as how to read longer DNA snippets or in developing precise instruments
to perceive fluorescent light.
"Honestly, it's going to take us 10 or 15 years to get
there," she said of the $1,000 genome. "The non-scientific
public is hearing this and saying that sounds really great, and people must be at that goal because they're talking
about it. That's totally not the case. This is the plan for the future, and the future is not now."